I know 'Saban' is viewed as a dirty word in most of the CFB landscape, but I have heard from a few different reliable personal sources that the nail in the coffin for him deciding to hang it up was after the loss last year, when he got to the locker room, instead of a fired up locker room talking about how they're going to never let this happen again, yadda yadda yadda, he had freshmen who had played exactly zero minutes that season asking "How much am I gonna get paid to stay?" A lot of his approach was getting young players to put in the effort to get better to 'earn' a spot on a big-time roster, but if the only motivation is the dollars in their pocket, they're not going to be willing to put in the sweat equity to earn a spot.
I also heard directly from a former D1 player friend that was invited back to visit his former program (not Alabama, but a similar level top-tier D1) say that the locker room atmosphere was nothing like when he played just 10 years ago. He said the comradery among the team was gone. All people were talking about was the money they were making and what they were going to do with it - there wasn't a sense of pushing each other or a sense of being in the 'fight' together. A couple of guys had gotten roasted by the coaches during practice and as soon as they hit the locker room all they wanted to talk about was where they would transfer.
My 13 y/o son and I were talking about it driving home from basketball practice the other night. We think that if things keep going as they are now:
1. Historical rivalries will fade away because the players on the teams have no history with the program, thus no personal loyalty to seeing their side of the rivalry win. And if they get beat like a drum, they'll just transfer to another program and not have any drive to 'get 'em back next year'.
2. The motivation for 2 and 3-star recruits to go to a big program and try to get better will go away - you may work 3 years at your position to grow into the starting role, but then BAM a booster throws some $$$ at an NIL deal for a transfer to come in and take the spot that you've 'earned'. Work ethic in the big-money programs will decline drastically.
3. The distance between the 'have' vs. the 'have-not' programs will grow far more than it ever has. They should probably just go with a 'Tier-1' league and an 'everybody else' league based on your NIL payroll. At least give the non Tier-1 teams a chance to compete and grow their programs internally.