He's also never left a coaching job early. You're talking about a guy who grew up not only in Ann Arbor, but with a dad coaching for UM and around the program and on the field for most games as a kid. That sticks with you. So much so that he was instantly committed to play there as well.
He was not going to get offered the Michigan job in 2007 over Rich Rod considering all he had was 3 years at a FCS school. Stanford was willing to take him and he did great. When his contract with Stanford was up and Michigan fired Rodriguez that was the first stirrings of "WE SHOULD GET HARBAUGH". He ended up choosing to coach in the NFL and did that well, too. Then after being forced out by awful management it happened to align with Michigan firing Hoke. All we heard was how Harbaugh isn't leaving the NFL, how he's determined to win a Super Bowl, how his family loves California and will not move to Michigan etc. only to have him in Michigan seemingly enjoying coaching more than ever. Don't forget he actually took LESS money than what Michigan offered to come here so they could pay for good assistant coaches as well. He also could have had any open head coaching job in the country that he wanted college or pro. He's completely revitalized the program and quite frankly the school and has done more in 1 season than Hoke and Rodriguez did in their 7 seasons combined.
"There are no turnarounds at Michigan. This is greatness. Long tradition of it."
"Throughout my life I have dreamed of coaching at the University of Michigan".
His previous stops were opportunities he took. He has not had any sort of connection to any of his previous coaching stops as he does to Michigan. Bo Schembechler meant so much to Harbaugh. I think Harbaugh leaving a legacy at Michigan that can be put up there with the likes of Fielding Yost and Bo is truly something he wants to do. Could he outwear his welcome? Only time will tell. But as long as he's winning people won't care and I think it's "crazy talk" to imply Harbaugh will leave prior to his contract (7 years) or that if he does leave it will be on his own accord. If anything he just can't get it done and leaves/gets fired which I don't see happening.