I think the ratings are a function of a couple of things:
- Fatigue: Yes, football is wildly popular, but the amount available to watch is so much larger than it used to be. Plus, Bowl games used to attract huge numbers because traditionally there was a 4-6 week layoff between the regular season ending and the Bowls. That's not the case anymore. With conference championship games, the regular season extended out for some programs and earlier and earlier bowl games, there's no gap there anymore.
- Diminishing luster of "big games": Remember how HUGE tOSU/Texas was in 2005? It was a matchup between two traditional powers who didn't play each other. It was an event. Bowls were an opportunity to see 2 schools that ordinarily wouldn't face off. Big OOC games were an attraction. Now, with these "super conferences", these matchups happen routinely and it's watered down everything else.
- Mounting frustration with the state of CFB in general: I've said numerous times, I now consume a fraction of CFB that I used to. My Saturdays were spent watching CFB all day for much of my adult like until a couple of years ago. Now, honestly, pretty much all I watch is tOSU games, and frankly not even all of those like I did for years. The transfer portal, NIL, and all of the ridiculous realignment has eroded the charm that CFB once had. It just feels like another pro league at this point and I think that's taking a toll.