If Fox wanted to produce a big game at noon, they can put it on Fox Sports 1. Enough people have more than just local channels that it won't make a difference.
The purpose of primetime scheduling for various things is to actually try and win the primetime ratings battle. Fox doesn't purposely schedule low-quality programs on any other night of the week especially during college football season. Saturday nights have evolved to the point where the only new things regularly airing on these nights anymore are usually sports events or on CBS, 48 Hours.
If Fox wanted to win the Saturday night ratings battle over ABC on Thanksgiving weekend, then they can't do things like they did in 2018. Consider this - ABC's SaNF broadcast of ND-USC was in the top 10 most watched regular season CFB games. Fox's competing broadcast of 6-5 Oklahoma State and 5-6 TCU was not, even though TCU plays in the same county as an NFL team which draws high ratings for Fox frequently, the Dallas Cowboys.
And while UM-OSU was #1, it potentially could have drawn more than 20 million viewers, even approaching Super Bowl viewership levels, had it been played at night. If Fox were willing to go along with UM-OSU being at noon that year, then they should have insisted on airing ND-USC in primetime instead of letting ABC have that game, which could have allowed eventual NCG winners Clemson to host the final on-campus SaNF game of 2018, the rivalry game against South Carolina, putting that rivalry on network television for the first time since 2000, when it aired regionally on ABC, and thus putting the OKST-TCU game on ESPN at 7 (where it should have gone, since it was not worthy of a primetime slot on Fox).
And AAK, you have it wrong. No real OSU fan wants to keep the game at noon. As I said before, a nighttime UM-OSU game going into multiple OTs well past midnight would be a real treat.