There’s no one explanation for how Game of Thrones became a culture-spanning phenomenon. Slipping into the microscopic gap between the Golden Age of Television and Peak TV, HBO’s fantasy epic earned an investment of resources from its network that would have been unthinkable previously for such a budget-conscious medium. Primed by group analyses of phenomena like The Sopranos, audiences gave the show their sustained focus and thought, a school of TV-watching still new enough for disciples to be disarmed by Thrones’ signature reversals. And in the culture at large, Thrones arrived at a time when genre storytelling was shifting from the margins to the center. The series premiered just three years after Iron Man inaugurated the Marvel Cinematic Universe, and will air its final installment as Avengers: Endgame maintains a weekslong stranglehold on the international box office.

But the simplest factor in Thrones’ success is also the most important. Quite simply, Game of Thrones is a good and influential TV show because it’s based on good and influential source material: George R.R. Martin’s A Song of Ice and Fire, the five-volume-and-counting saga that first originated the Stark and Lannister clans back in 1996. Since Thrones creators David Benioff and D.B. Weiss bypassed Martin’s original material circa Season 6, the relationship between books and show has complicated. My colleague Ben Lindbergh declared Martin the “real winner” of Thrones’ much-maligned seventh season, vindicated even in his writer’s block by the creative choices being made on his behalf. (In theory, A Song of Ice and Fire will have two final volumes, bringing the total to seven; Martin has not published a new entry since A Dance With Dragons in 2011.) Having once so masterfully adapted Martin’s vision to the screen, Benioff and Weiss began encountering a much more public version of his same difficulties in bringing their shared story to a close.

With its cast of thousands, dense mythology, and intercontinental scope, A Song of Ice and Fire is an awkward fit for the screen indeed. Yet what the current split in regard between books and show tends to obscure is that this very awkwardness was once a boon, not a handicap. Nor is A Song of Ice and Fire as distinct from television as this dichotomy tends to imply. Game of Thrones exists, by its nature, in conversation with the books. From their beginning, however, the books themselves were in conversation with TV. Keeping this origin story in mind, Game of Thrones’ struggles as it comes to a close this Sunday are less a divergence than the closing of a full circle. A Song of Ice and Fire was an explicit reaction against television, which made its adaptation inherently subversive TV. And what some have interpreted as Game of Thrones shedding the qualities that once made it exceptional is, in fact, a capitulation to its format. Game of Thrones may be the biggest television show of all time, but at the end, it couldn’t transcend television.

From the mid-1980s to the mid-1990s—right around the time A Game of Thrones was published—Martin lived in the belly of the beast. Like many novelists before him, Martin went Hollywood, writing for the first revival of The Twilight Zone and serving as a writer-producer on CBS’s Beauty and the Beast. When he tried to launch some of his own projects, Martin quickly ran up against the limitations of an industry he was decades too early to disrupt. “The theme of that whole period for me was, I would always turn in my first draft to whatever network or studio or producer I was working for and the reaction was inevitably, ‘George, this is great. It’s terrific, it’s a wonderful read, thanks. But it’s three times our budget. We can’t possibly make it. It’s too big and it’s too expensive,’” Martin told The New York Times in 2011, ahead of Thrones’ premiere.

Enter the written word. “When I returned to prose, which had been my first love, in the ’90s,” Martin continued, “I said I’m going to do something that is just as big as I want to do. I can have all the special effects I want. I can have a cast of characters that numbers in the hundreds. I can have giant battle scenes. Everything you can’t do in television and film, of course you can do in prose because you’re everything there.” Martin subsequently took full advantage of the freedoms experience had taught him to appreciate. Without a time slot, he populated Westeros with noble houses served by smaller houses served by peasants protected by sacred orders. Without budgets, he plunged the continent into a five-front war. And without actor contracts, he killed his main character and several of his potential replacements, egos and agents be damned.

Ironically, such blatant defiance of television’s institutional norms makes for inherently interesting television. To its credit, Game of Thrones didn’t change the core characteristics of A Song of Ice and Fire to make them more palatable to TV. Instead, it was TV itself that was changed. Never before had a show baited and switched its audience about the very concept of a protagonist; never before had a show included hourlong battles with the financial demands of a feature film; never before had a show carried such an overwhelming mass of detailed lore that it could single-handedly support its own explainer industry. Part of what Thrones’ legions of fans have responded to is old-school craftsmanship, in the form of great performances and richly outlined characters. Much of the appeal, however, was novelty: Viewers weren’t used to feeling the disorientation that came with Ned Stark’s beheading or Jaime Lannister’s gradual redemption, so they stuck around for more.

The sheer feat of translating these subversions, and balancing them with the practicalities necessary to create an actual television show, ought not to be understated. Whatever criticisms they’ve faced for their relatively original storytelling, Benioff and Weiss proved themselves to be master adaptors. Without Martin’s device of limited third-person, point-of-view chapters, which could transform a character from caricature to de facto narrator in an instant, Game of Thrones capably planted the seeds of the Lannister twins’ nuance much earlier on. Without pages’ worth of raw exposition, Thrones re-created the feeling of Westeros as a place buckling under the weight of its own history, haunted by the phantom pains of a war decades in the past. This accomplishment alone places Thrones in the pantheon of series that fundamentally altered audiences’ expectations of TV.

A cruel paradox of Thrones’ later seasons, then, is that the show effectively trained its fan base to hold it to the same logical, methodical, unsentimental standard as the earlier seasons and books did fantasy tropes. A decade ago, A Song of Ice and Fire so effectively commented on sword-and-sorcery mainstays it changed how some readers saw the genre; now, Game of Thrones has preemptively taught its viewership to reject the shortcuts and workarounds it’s taken on the way to Sunday’s conclusion. Because many of the flaws in Thrones’ home stretch aren’t unique to Thrones. They’re products of typical TV logic—exactly the kind Thrones initially rejected, and can no longer resist.

Notoriously, seasons 7 and 8 of Thrones have been condensed down to just seven and six episodes apiece, as opposed to the show’s usual 10. This decision, which Benioff and Weiss have taken full responsibility for in interviews, made itself felt immediately—and detrimentally—in the rhythm of the show. Journeys that once took entire seasons, and yielded pivotal bonds between unlikely character pairs such as Jaime and Brienne or Arya and the Hound, suddenly took less than an episode. Key scenes, like Jon Snow disclosing his Targaryen ancestry to his adopted siblings or a potentially fruitful conversation between Tyrion Lannister and Bran Stark, were skipped over entirely. Major plot developments, including Jorah Mormont’s recovery from greyscale and Viserion’s transformation into an ice dragon, were practically handwaved.

For a story where structure and substance are as tightly interlinked as Thrones’, these logistical considerations quickly took a toll on characters and themes. The most recent example of Thrones’ newfound speed undercutting its former methodology is also the most controversial: the rapidly manifested, unconvincingly indiscriminate genocidal tendencies of one Daenerys Targaryen. Longtime observers’ understandable impulse was to contrast such hasty pivots with Thrones’ earlier world-building. Yet it’s equally revealing, and useful, to point out how similar Thrones has become to more familiar forms of television as it is to point out how dissimilar it’s become from itself. Even if Thrones’ impending deadline is self-imposed, hurtling toward a destination determined by outside circumstances is classically TV. The lead got a better opportunity, so they need to be written out of the show; the network canceled the series, so every loose end needs to be tied up on someone else’s schedule. In theory, Thrones enjoys unlimited resources to destroy fictional cities and animate undead armies. By running short on time and taking obvious steps to overcome this shortcoming, however, Thrones has found itself in the same strained, resourceful state as countless shows before it.

Not all of Thrones’ concessions to television’s unspoken bylaws are purely logistical. One of the books’ defining trademarks is a rigid obedience to the demands of the story over the wishes of the reader. Like its epic scale, this principle was an antidote to ratings-ruled TV, whose audience had the power to demand to be catered to and could vote with their remotes if they weren’t. Thrones’ ubiquity has been long since secured, but its final seasons have been marked by the kind of fan service, wish fulfillment, and endgame-driven decision-making its earlier iteration scrupulously avoided. Potential fatalities, including those of virtually every major character in a battle we were later told eliminated half its combatants, were miraculously avoided. Popular pairings, like Brienne and Tormund’s one-sided flirtation, were forced to the point of outliving their initial charm. Fairy-tale-like happy endings were seemingly provided (though Sam’s paternal bliss or Tormund’s riding off into the sunset could well be undone in the finale). Certain conflicts, like Varys’s betrayal of Dany in favor of Jon, occurred not because of past events, but because they needed to in order to justify future ones.

Thrones remains a powerhouse, and the achievements of its foundational first half will endure. But just as Thrones’ heroes have found that they can’t overcome the sins of their ancestors—madness on Dany’s part, honor-bound naivete on Jon’s—Thrones itself has run up against the precedents it once upended. Game of Thrones has an awareness, and wariness, of its form built in from the jump. Sometimes, though, one’s natural instincts take over, especially in the absence of an author’s guiding hand. The long arc of serialized television bends, inexorably, toward itself.

Disclosure: HBO is an initial investor in The Ringer.