If true - he must really, really hate it here/or have created a wildly toxic environment… not sure there’s another reason you’d take a step down when a conference title is possible and would almost certainly come with an extension.
Legal stuff. The conference championship game is considered part of the regular season in contract terms. If CH admits he has taken another job now, MU can screw him out of paying his various bonuses. You will see an announcement next Sunday.