All it took for the SEC to take a step back was NIL and the transfer portal. Now that everyone else can pay players, there is much more parity in college football.
Same for the transfer portal, now players aren't wanting to be the second or third stringers at Georgia- they transfer to another school and then that school has a better chance at beating Georgia (like GT).
Take Vanderbilt, for example. Their team and coaching staff straight up imported New Mexico State's staff and best players (you remember, the team that beat Auburn), including their starting QB. Now Vandy beat Alabama this year.
The SEC is still the best conference in football by Sagarin ratings, but it isn't the world beater that it was in previous years.