When he was at Boise, one of his children was fairly young at the time and had medical issues, I believe. It was thought that was the reason he spurned many offers to leave there and might never take a P5 job, but he did eventually go to Washington. I seem to remember the narrative being that he'd never leave Boise, or would never leave the PNW.
Petersen reminds me a lot of Mark Richt. An extremely professional, buttoned-up guy and the job wasn't the end all, be all thing in his life. Loved coaching football, but also had other interests/things that are important to him. It's a stark contrast to most CFB coaches, where it is like 99% of what they know and care about is football. IMO, you kind of have to be an a-hole to be a high-level CFB coach, and he definitely did not seem like one.