At the end of the day it always comes down to money.
Football, at the FBS level, no longer plays for an NCAA championship, they play for the CFP championship so the P5 conferences can control the majority of the money.
The NCAA makes $1 billion/year from the basketball tournament and shares about 50% of that with the member schools which includes all D1 conferences.
What if a network offered the P5 $400MM for a 24 team tournament? Of course people will complain that it's not 68 teams like it is now or, that it eliminates the chance for George Mason to go on a Cinderella run but, the P5 Commissioners and AD's don't care about that, as they've all demonstrated for years. All they care about is how much money will it generate. If it's more than they make now it becomes an easy decision.
The breakaway has already happened for football because of money. To think that it won't happen for basketball, with all that money on the table, is naïve thinking