You could be right, he probably wants to go back to the NFL.
The 49'ers in their infinite wisdom, did not want to deal with Harbaugh because he wanted more power. So, they realized that they didn't need him anymore, because they knew they could get back to the Super Bowl anytime they wanted, because they had a team full of stars, especially at QB. What could go wrong?
I don't have the issues with him than most fans do. Yes, losing to Michigan State is maddening. Although that fluke win because the Punter dropped the ball is not on Harbaugh. Losing to Ohio State all the time is even worse, but that's how it goes.
Again, I remember the Rodriguez & Hoke tenures, although I thought Hoke tried his best, and Harbaugh has gotten Michigan to win more games against teams that they should beat.
Yes, I want the Wolverines to be in the playoffs every year and I want to win multiple National Championships. I still do not count 1997, because that was a split title and the coaches only gave it to Nebraska because they wanted to give Tom Osbourne a goodbye gift.
For now, I'm fine with Harbaugh staying. When he does leave, I don't think he will screw Michigan, he will have the right person ready to take over.