i think there are a few factors here.
Bama being in the game is probably the biggest one. To some extent even OSU. People are just tired of it. You see this behavior from fans in other sports, they just ignore it when they already know the likely outcome.
Social justice splattered all over everything on and off the field. like it or not, this does have an impact on viewership. (please don't make this political fight, its just a analysis of viewership patterns).
Cable cutters. this is becoming a bigger and bigger thing, combine it with the pandemic and some of those folks that would go to a bar to watch the game and you lose some amount of viewers. 6.6 million people dropped cable tv in 2020, a 7.5% drop in cable subscribers. combine that with streaming services being launched and content providers only releasing new content on the streaming platform and not cable tv, ppl are saying why get cable at all. (note, im one of those ppl, i see my cable bill and ask myself what does this give me?, answer is very little)
Note: for anyone interested, history channel releases full episodes of some of their programs every day on youtube for free. their full episodes playlist currently has 894 videos in it.