CAVEATS: I'm not BamaCoug or krindorr and the data set is just 2021. I excluded Thanksgiving weekend, Conference Championship weekend, and Bowl Season as those aren't "normal." There is no data available for CBS Sports, Pac12 Network, Peacock, or FS2; ESPNU data is also sparse.

I looked at TV Viewership numbers for 2021 by Network and time slot and noticed some interesting trends (any network/slot combinations with 3 games or fewer was eliminated since it's more of a filler of time than a designed strategic time slot).

Ranking Networks/Time slots:
#1 ABC Saturday 7:30pm ET, averaging 4.9M viewers; a lot of Big Ten and SEC games here (or Big 12 involving OU; Pac 12 involving UO).
#2 CBS Saturday afternoon (usually, but not always, the SEC's top game), averaging 4.8M viewers.
#3 Fox Big Noon Kickoff (usually, but not always, Big Ten #2 game), averaging 4.7M viewers.
From there it's a decent-sized drop-off:
#4 ABC 3:30pm at 3.5M viewers.
#5 ABC Noon ET at 3.2M
#6 Fox 3:30pm ET at 2.9M
#7 ESPN 7:30pm ET at 2.8M
#8 NBC/ND 3:30pm ET at 2.4M (NBC didn't have enough 7:30pm ND games to "qualify" for this analysis but averaged 2.6M in 2 games)
#9 ESPN Noon ET at 2.1M
#10 Fox 7:30pm ET at 2.0M

The Pac 12 slots:
****#11 ESPN FRIDAY NIGHT at 1.6M
#12 Mandel's coveted ESPN 10:30pm ET at 1.6M****
Mandel claims those late night games are "so hot right now" but ESPN Friday night was the #11 time slot and Saturday late night was #12 in terms of average viewership. Those slots do outperform ESPN 3:30pm ET kickoff, which has to compete with #2/#4/#6 on the Over-Air Networks. The ESPN2 Saturday late night slot was #26 of all timeslots with more than 3 games over the course of the season; it ranked even lower than MAC-tion on Tuesday/Wednesday night.

Why Disney wanted SEC so badly:
Disney had the #1 slot and CBS/SEC was #2 slot. However, with the news out now of them losing the Big Ten contract they are losing a lot of the inventory that made slots #1/#4 so highly viewed, and replacing it with 1 SEC game/week that they didn't get before.

Top 5 games each week:
Only 5 of the 60 games that were Top 5 in its respective weekend had two teams where neither will be in the B1G/SEC in two years (as it stands today). 3 of them involved Oregon in conference games. The other 2 involved ND (vs FSU on Labor Day Sunday and Cincinnati).
Utah showed up once (against Oregon). BYU got up to #6 against Boise. Some surprises that showed up in the Top 5 most watched games in a weekend (mostly due to their opponent): Purdue x3, Rutgers, Colorado x2, West Virginia, Indiana x2, TCU, Illinois, and Iowa State x2. So if you play Ohio State, Michigan, Notre Dame, Oregon, or Oklahoma, you have a good chance of making the list.

1M Viewership:
ABC (37 games) and Fox (32) had every single game reach 1M viewers.
CBS had 14/15 with the lone miss: Boise State at Utah State which netted 0.8M viewers.
ESPN had 1M viewers 74% of games (50 out of 68)
ESPN2 at 17% (9 out of 54)
Big Ten Network at 15% (4 out of 27)
FS1 at 9% (4 out of 44 games)

3M Viewership:
73% of CBS/SEC games hit 3M (11 out of 15)
62% of ABC games did (23 out of 37)
50% of Fox games did (16 of 32)
15% of ESPN games (10 out of 68)
17% of NBC/ND games (1 out of 6).

Impact of Conference Realignment:
CBS will obviously drop unless they can get high Tier 2 Big Ten games or #1 Big 12/Pac 12
ABC should hold flat/slightly increase (as they replace highly watched Big Ten games with one additional highly watched SEC game)
Fox should increase as they will now get all the higher profile Big Ten games.

Other Networks don't matter, at all:
Once you drop below ABC, CBS, ESPN, and FOX people just aren't watching you. MAC-tion games on ESPN2 draw the same viewership as FS1 at any point on Saturday and better than the ESPN2 late night Saturday games.

BYU's Performance:
BYU performed fairly well vs the average generally speaking but had some glaring weaknesses, trying not to be too blue-goggled but I'd venture the competition had as much to do with that as anything. The Arizona game is one that missed the mark as only 2 other games all season in that time slot did worse. The Boise State game was the 2nd worst performer on its network/time slot (GT/Clemson, which was delayed for inclement weather, was worse) but it was also the ONLY game all season in that time slot that didn't have two P5s playing (so you could argue it's a miracle BYU/Boise even got that slot). Washington State game was also pretty bad but there was a general boycott by Wazzu fans after their coach was fired that week for not getting vaccinated...
Otherwise BYU was pretty much right around the average viewership for a time slot/network combination. Virginia was probably the one "over-deliver" based on times and network at 200k (42%) higher than average.

Just for fun...Utah's Performance:
BYU-Utah was average in the timeslot/network
Utah-USC was over 600k below average in the timeslot/network
ASU-Utah was slightly below average (and below ASU/BYU and Utah/BYU in the same timeslot)
UCLA-Utah was about half the average viewership for the timeslot
Utah-Stanford was 452k viewers which was 75k/21% above the average...
Oregon-Utah was slightly below (the very high) average viewership for the timeslot
So Utah was below average pretty much every game where it wasn't relegated to the P12 Network. Yes, a lot of people watched the Rose Bowl but, based on other evidence presented here, I think it's safe to say that Utah had nothing to do with it (I know the average CBer knows this but not all the Ute fans on here realize it).