We are all speculating here, and I suppose that's dangerous. Did he "mail it in"? I don't think so. Did he give the level of effort needed or that he has provided previously? I don't think so. There have been many anecdotal bits of information that suggest that he simply isn't working as hard as he did early on as coach.
But I'm not going to focus on that, because regardless of whether he tried to do his best, his best wasn't good enough. He couldn't figure out which of his own players were good and would give the team a chance to win. His offense has all the sophistication of a playground pick-up team, and the defense isn't much better. His team started slow almost every game...and to me eyes, looked like they had little to no preparation for the opponent. They would leave good shooters open and guard guys who were not threats. Their adjustment to that in game, was painfully slow, if it every came.
UConn needs the buyout to be a small number. It can't worry about Kevin's well being in that regard. He had made a lot of money from UConn and the NBA, enough that, divorce or not, he shouldn't need to work. He's also very employable as a coach, presuming he doesn't let his reputation be harmed by a protracted fight here. Both sides should want this concluded quickly.