NEW ORLEANS — The signs of a renewed football empire were everywhere as Monday night merged with Tuesday morning: the cigar smoke cloaking Louisiana State’s locker room, the purple and gold confetti on the Superdome’s field, the crush of reporters and state troopers surrounding a coach whose career had been all but left for dead not long ago.

On Monday night, L.S.U. — a program that just two years ago failed to beat Troy, a team it paid nearly $1 million to play — again reached a single-season pinnacle. But the recent history of college football shows that L.S.U., which began this season as an underdog even within its own division, faces a mighty challenge in keeping its toehold at the very top.

“Everything fell into place to have the season we needed to have,” said Ed Orgeron, the Louisiana native who grew up harboring a dream to coach the Tigers.

Since the start of the Bowl Championship Series era in the 1998 season, which ultimately gave way to the College Football Playoff system in 2014, a champion has successfully repeated winning the crown just once: Alabama. But L.S.U. has now amassed the second-most titles of that 22-season stretch — more than Florida, Ohio State, Oklahoma, Southern California or, yes, Clemson.