Shawn Mendes in New York. (Photo by Drew Gurian/Invision/AP)

Shawn Mendes has a voice like a middle-school glee-clubber, a face like a younger, less pug-nosed Bieber, and a croony, largely acoustic oeuvre that’s big on sensitive smolder and cutesy cliche.

As of this week, Mendes also has the best-selling album in the iTunes store — thanks, in very large part, to the legion of teenage fans who propelled the 15-year-old Vine star out of social media obscurity and into the mainstream in fewer than 40 minutes. Haven’t heard him yet? You will: Earlier this month, the Canadian singer became the youngest artist to debut in the top 25 on Billboard’s Hot 100 — and that was before he had released an actual album (he’s signed to Island), or gone on tour (on Wednesday night he opens in L.A. for fellow teen idol Austin Mahone).

“This kid is a superstar!” Island’s talent scout, Ziggy Chareton, told Billboard in June. “[We needed] to move really quickly. His social presence is huge.”

Mendes is not the first or only Vine star to reach mainstream fame — Nash Grier, Cameron Dallas and the poorly named Us come to mind — but he may be the best example of how powerful a platform Vine has become. To outsiders, the network can be impenetrably insidery, even inane: six-second snippets of high-school humor, contextless memes, and other trendy ephemera you’d struggle to explain to anyone over 25. (Notably, a rundown of the current Vine scene in The Wire has classified each “Vine star” according to how old he’d make the reader feel.)

But that insularity only disguises the fact that Vine is really, really huge — a cultural force that can spin celebrity from just a few seconds of teen antics or angst. While the platform hasn’t released statistics on its user base since last August, evidence would suggest its monthly users have climbed well into the tens of millions; per AdAge, nearly a dozen tweets with a Vine attached are sent every second. That audience helps explain the meteoric rise of “Vine celebrities” like Grier and Dallas, who are working with a DreamWorks subsidiary on their first film, and Us, the husband-and-wife folk duo who signed to Republic Records in March.

Mendes certainly wouldn’t have released his EP without the network — the Ontario high-schooler, who had posted cover videos on YouTube since middle school, spontaneously gained 10,000 followers on Vine when he uploaded a cover of Justin Bieber’s “As Long As You Love Me.” From there, his increasingly rabid social media fan base pushed him into the ranks of Vine stars, onto the MagCon Tour — a cultlike circuit that puts (teenage, male) social media celebrities in front of their (teenage, female) fans — and, eventually, into the inboxes of managers and talent scouts at Island, a Universal subsidiary. He signed to the label in June.

This is, as many commentators have previously said of Youtube stars, a total inversion (and democratization) of the traditional path to stardom. After all, some of Mendes’s closest contemporaries on the iTunes charts — like Meghan Trainor, who is 20 — grew up with musical families, in-home studios and years of professional lessons. But Mendes was just a former glee club kid in Pickering, Ontario, without any significant connections besides his smartphone’s data plan.

That would be more heartening, perhaps, if Internet fame weren’t also so inescapably random. Merit plays a part, sure. (One needn’t watch more than the first few seconds of Mendes’s first single, “Life of the Party,” to believe he was put on this earth to make 14-year-olds swoon.) But thousands of high-cheekboned teenage boys strum guitars at their camera phones on the daily, and few of them have record deals. Why Mendes? Why did his August 2013 cover of “As Long As You Love Me” — which is cute, but not much else — attract a whopping 10,000 likes overnight? At some level, it’s all luck and chance and well-timed cascades of sharing, like pretty much anything that goes viral online.

Even Mendes himself seems to realize that: Interviewed by Billboard in June, he described his reaction to that sudden fame with a very teenage locution — “Whoa.”

But what other reaction could there be, really? A series of six-second videos, and a multitude of teenage girls, have elevated an otherwise unremarkable amateur to the very top of the iTunes charts. That’s incredible. It’s kind of powerful, really. And increasingly, it would seem, that’s the way the music industry — maybe all of pop culture — works these days.