For years, Chris Stapleton had been an unstoppable force in Nashville — but one working mostly behind the scenes as a songwriter and member of his bluegrass group the Steeldrivers, letting others take the limelight with his words. Writing for everyone from Patty Loveless to Luke Bryan, he gave country music a lot of its heart, soul, and southern-rock swamp from the early 2000s on (yes, even for Luke Bryan). But on his 2015 solo debut, Traveller, Stapleton broke all the norms: He found stardom in his thirties, put country music — not pop country or bro country — back on the map, sang with Justin Timberlake, and sold millions of records in the process. He’s now not only one of the genre’s biggest stars, but he’s managed to create a wave of interest in country traditionalism in his wake.