By the fall of 2014, “Turn Down for What,” Lil Jon and DJ Snake’s triple-platinum trap-meets-EDM single had swallowed pop culture whole. Jimmy Fallon and Robin Wright were dancing to it on The Tonight Show; Jonah Hill and Channing Tatum posed while it blared on the soundtrack of 22 Jump Street; across YouTube, teens and kittens alike bobbed their heads along. Spin called it “an undeniable force.”