INDEPENDENCE is most likely the biggest factor. Bronco told Ian Fitzsimmons that it was the #1 reason he left.
Yeah, coaches wanna get paid, but these are all alpha-male dudes who also want to win. They want to be the best. They want their names in the history books. And BYU isn't going to get them there.
As long as BYU is Indy, they'll never achieve a special season.