Given how much ink has been spilled about solving the whodunit featured in the new podcast “Serial,” let’s tackle an equally confounding mystery: How on earth did a podcast become such a pop-culture sensation?

Episodic digital audio programs like “Serial” have been around for nearly a decade, but have remained something of a fringe attraction at best. But with its exhaustive dissection of a 15-year-old murder case in Baltimore, “Serial” has scored a breakthrough (not to mention a second season order). In addition to netting 5 million downloads and streams in record time, the podcast is analyzed and satirized with the kind of fervency typical of a hit TV series.

Naturally, there’s plenty of speculation that “Serial” will be adapted for TV or film. But that’s not in the cards just yet, according to its creators at WBEZ Chicago, which produces another great oral storytelling franchise for radio, “This American Life.” Regardless, you can bet “Serial” will end up adapted for another medium.

Just don’t be so sure it will be successful. And the same doubt can be cast on podcasts, which are seemingly poised on the verge of an explosion in popularity.

“Serial” is the story of Adnan Syed, a high school student who was sentenced to life in prison after being convicted of strangling his ex-girlfriend, Hae Min Lee. What might seem a run-of-the-mill crime of passion is transformed into a compelling saga by narrator Sarah Koenig (pictured above), whose exhaustive dissection of the case raises so many questions that the guilt of Syed seems far from clear.

It’s a fascinating story, but here’s where “Serial’s” success becomes a mystery in its own right: The podcast is really no more or less engrossing than the countless other true whodunits common all over movies and TV. Even an average episode of a relatively low-profile TV staple like NBC newsmagazine “Dateline” routinely features cases like Syed’s; you could even argue recreating these crimes for TV is a more sophisticated form of storytelling.

So why has “Serial” become such a phenomenon? What elevates this podcast above the many others that have covered similar ground is the fresh spin Koenig puts on the genre through the tone of her narration. Instead of the standard dispassionate style that doesn’t seem to have evolved much from Jack Webb’s leaden delivery on the 1950s TV series “Dragnet,” Koenig takes a more human, even folksy approach to recounting the case. She injects her own doubts, foibles, even sarcasm through every twist and turn in a manner unlike the way a whodunit is typically treated.

For the Hollywood producers who have already begun circling “Serial’s” TV or movie rights, this facet should give them considerable pause. It’s not entirely clear how Koenig’s style, which is so perfectly matched to the intimate nature of podcasting, could work in another medium. That said, if you’re anybody from CBS’ “48 Hours” to Investigation Discovery’s “A Crime to Remember,” letting “Serial” inspire a shakeup to the conventions of this genre isn’t a bad idea.

The lesson podcasters should learn from “Serial” is so obvious that you can criticize its practitioners for not having tried it earlier on: the whodunit format that is already such a reliable draw in TV and movies works well here, too.

The problem with “Serial’s” success is that it won’t represent an inflection point for podcasts for one simple reason: Even if the hype for this show grows to a level where it brings podcasts exposure to a new audience segment perhaps even more sizable than that of current core podcast devotees, there’s little else like “Serial” for this wave to listen to that will keep them around to sample more content.

If the podcast biz is smart, that will change very quickly. Surely there’s an entrepreneur or three out there who realizes that “Serial’s” formula — applying Koenig’s storytelling style to the crime genre — is easily replicable. It’s no different than the way each TV pilot season becomes rife with projects that borrow from the themes driving whatever is the medium’s hit du jour. Until then, podcasting still represents a rather immature category.

It would not surprise me if in retrospect “Serial” is remembered in a manner of another half-forgotten marvel of digital storytelling: Lonelygirl15. When this interactive video gem first rose to prominence back in 2006, it too was hailed as such a trailblazer that many predicted it would birth a whole genre of mass-appeal online programming. And while Lonelygirl15 bears some influence on the Web content that followed, its promise was never really realized. As with “Serial,” its greatest strength is essentially its greatest weakness: Lonelygirl15 was too unique to be replicated.