Young audiences turned out in droves to movie theaters around the country this weekend. It wasn’t for the big budget “Star Wars” movie, “The Mandalorian and Grogu, ” which fell sharply in its second weekend, however, but for a small budget horror from a 20-year-old first-time filmmaker that began on the internet.“Backrooms,” released by A24 in 3,442 locations in the U.S. and Canada, made an astonishing $81.4 million in its first three days in theaters, according to studio estimates on Sunday. That’s just a few hundred thousand dollars shy of what “The Mandalorian and Grogu” earned in its first three days last weekend; And “Backrooms,” which was directed and co-written by YouTube creator Kane Parsons, cost only $10 million to produce. The wild success of “Backrooms” didn’t even hurt “Obsession,” which is also the directorial debut of a YouTuber, Curry Barker, who is only 26. Three weekends in, “Obsession,” a movie that cost less than $1 million to make, still hasn’t dropped below its opening weekend earnings. This weekend, it was up 10% with another $26.4 million for a second-place finish, leaving Star Wars, the legacy franchise movie from the veteran filmmaker and the Walt Disney Studios, in third with $25 million.