The breakout hit of the fall TV season is a quiet family drama that looks like no other breakout hit in TV history.

When NBC’s This Is Us debuted in September, its series premiere scored more than 10 million live viewers (people who watched it either as it aired or on their DVRs that same night), and the show has yet to fall below 8.5 million viewers, with most episodes cresting 9 million viewers — that’s really stable in an age when even big hits see big declines from their premieres. (For comparison’s sake, The Big Bang Theory, one of TV’s most-watched scripted shows, draws a little over 14 million viewers.)

Even better for NBC, This Is Us’s viewers skew young, with most falling in the advertiser-beloved 18- to 49-year-old demographic. Indeed, it’s routinely one of the top 10 shows in that demographic.

The series hasn’t quite had the rocket-quick start that broadcast TV’s last big hit, Empire, enjoyed during its first season, back in the first half of 2015. But that it’s proved to be a strong, steady performer — in a TV era when everything is crumbling — is a victory in and of itself.

And its success is especially surprising because, as mentioned, This Is Us is a quiet family drama, a genre that has been known to draw critical acclaim while suffering low ratings almost since the inception of TV.

From Family in the '70s to Parenthood in the early 2010s, quality family dramas have always struggled to find an audience commensurate to their quality. TV viewers tend to like life-and-death stakes, and family dramas usually don’t provide them.

So how has This Is Us managed to beat the odds? There’s no one single reason, but here are five contributing factors.

1) NBC scheduled the show well

TV scheduling "flow" — the way in which one program leads into the next — isn’t as important these days, in the age of streaming and DVRs, but it still counts for something. And NBC was smart to place This Is Us behind the Tuesday installment of its hit reality competition show The Voice.

But NBC did something even smarter when This Is Us debuted. It knew that the 9 pm hour — when This Is Us would have to face off against stiff competition like CBS’s Bull and ABC’s family comedies — would be more competitive than the 10 pm hour. So the network contrived to swell the Tuesday edition of The Voice to a two-hour extravaganza for the first few weeks of the season, thus pushing This Is Us to 10 pm.

Eventually, it moved This Is Us to 9 pm, but by then, the audience was already hooked, and its ratings have proved remarkably consistent ever since, to the degree that the show routinely wins its time slot in the 18-to-49 demographic. And the lineup of The Voice into This Is Us into Chicago Fire has given the network a solid performer at every hour on Tuesday nights.

2) It’s different, at a time when a lot of TV feels familiar

TV dramas are in a bit of a rut. Sure, there are still good ones out there — mostly on cable and streaming — but the boom of Peak TV means that the vast majority of dramas hit the same story beats and basic tropes. Either they’re "case of the week" shows with cops and doctors, or they’re high-stakes serialized dramas about antiheroes and/or folks working to save the world, frequently in the face of outsize or supernatural threats.

This Is Us is neither of those things. Yes, it’s serialized, but you can hop in and out without missing too much. Its characters are believable, recognizable people, played by a mix of actors you may already know and love from other TV shows and instantly ingratiating newcomers. And while the show’s "one family faces its problems head on" structure might not be unique across all of TV history, it is pretty new in terms of current primetime offerings.

Indeed, the show that This Is Us most resembles is probably ABC’s long-running comedy hit Modern Family — right down to the fact that the two shows have the exact same twist to end their pilots. (This Is Us just takes it one step further.) Finding the dramatic side of a popular comedy (or vice versa) is a long-running tradition in TV (CBS’s Scorpion is basically a dramatic Big Bang Theory), because it’s a good way to create something familiar but not too familiar. This Is Us pulled off that trick perfectly.

3) It’s stealthily episodic

This Is Us creator Dan Fogelman has talked about how one of the big influences on the show is Lost, ABC’s famous desert island drama about castaways whose lives prior to being stranded were just as eventful as their lives on the island itself.

Lost is frequently remembered as incredibly serialized, the kind of show you couldn’t miss a single episode of, and it was ... eventually. But at the start, its flashback structure — which dug into the past of a new individual castaway with every new episode — provided an easy way for viewers to stick with the show. Even if you couldn’t follow the mysteries on the island, you could follow that week’s flashback storyline.

So it goes with This Is Us, which uses a similar time-hopping structure to make sure there’s at least one closed-off element in every episode. But it might go even further than Lost, in the way it self-consciously structures its episodes as little short stories about particularly important moments or objects in the characters’ lives. That gives every episode a throughline for viewers to cling to, which is vital for recruiting new fans.

4) The show is more than "just" a family drama

This Is Us also borrows from its Lost influence in another key way: It loves twists.

Truth be told, the show’s embrace of twists and time-hopping gimmicks is what holds me back from fully embracing it. At times, the series simply lacks clear dramatic stakes, because it relies too heavily on storytelling trickery to save the day.

But, goodness, those twists have become a fun way for the show to keep audiences guessing. In retrospect, the idea of giving a family drama the same love of backstory that Lost boasted makes a ton of sense.

Families, after all, construct gigantic mythologies about themselves, full of inside jokes and constant retellings of important moments in family history. This Is Us simply mimics that behavior and weds it to the structure of a mystery show.

Can the show’s approach be irritating? Certainly, especially when vital information is withheld from the audience for absolutely no reason. But it’s also a great example of how TV is often best when disparate genres cross-pollinate each other. If you had said a year ago that one of the biggest new hits on TV would blend equal parts Modern Family, Parenthood, and Lost, most TV fans wouldn’t have believed you. But here we are.

5) The family drama audience has always been there. The difference is that it’s finally big enough to sustain a show.

If you look back at the ratings for Parenthood’s first season, they’re smaller than the comparable ratings for This Is Us, but not by all that much (especially in the 18-to-49 demographic). The higher viewership numbers for This Is Us can easily be explained as Voice overflow.

The shows’ ratings similarities indicate a strong "family drama" audience that always embraces this type of programming. Meanwhile, it’s likely that this audience was especially drawn to This Is Us by stars Milo Ventimiglia (of Gilmore Girls) and Mandy Moore (who’s starred in what feels like seven dozen movies with that "family drama" feel).

But even though that audience was never large enough to make Parenthood a hit, the rest of TV has collapsed so much in the past few years that a slight rise from the earlier show has made This Is Us the big new hit of the TV season.

This doesn’t mean that what This Is Us has accomplished is small potatoes. Launching any new TV show to success in this era is very, very hard to do. But to some degree, all hit TV shows succeed thanks to timing — and This Is Us was timed just about perfectly.

This Is Us airs Tuesdays at 9 pm Eastern on NBC. Previous episodes are on Hulu.