None of those departures included failure, firing, or premature departure.
Probably also wrong re: Tennessee (it’s never premature to leave an SEC cellar-dweller for one of the top 4-5 programs in CFB).
So now we’ve got the firings at Oakland and USC that, in retrospect, are probably more indicative of administrative mismanagement and dysfunction.
Your premise is demonstrably wrong, and, coming just after Dart’s decision, looks like sour grapes.