I'm not trying to get into an argument over something I don't care strongly about either way, but Dan Enos would be an interesting starting point for your question.
Won the Pioneer League at USD x2
Won the NFC championship with the 49ers
Won the Big Ten at Michigan
He did that without being on a front runner.
Gaddis is already a failure in your eyes.
He is doing charity work at Michigan because it's his alma mater. Michigan would look like UVA or Cal without Harbaugh. There is a reason his name keeps coming up for NFL jobs.