Could he see the writing on the wall and knew that independence wasn't sustainable, especially with the Utes getting into the Pac 12?

Did he just want a new opportunity?

Was he hoping for some appreciation and tired of an increasingly disgruntled fanbase? Was he tired of his family getting "abused" by "fans"?

Was it just wanting more money?

Was the administration wanting to force him out or threatening to non-renew his contract?

Personally I believe that Bronco had to deal with a whole lot of crap and he got tired of it and wanted to leave on his terms before he was forced out.