His son could transfer, so I think that argument is kinda silly.
I don’t see him as being scared either so I’m convinced he’s just not ambitious enough to want a HC job at this point. As someone with very little career ambition I could totally understand him wanting to focus on what he loves doing instead of all the administrative headaches that come with being a HC.
Yes, his son could lose a year of eligibility and transfer to a team that is a long ways for competing for a national or even conference championship. Only his son could say if that is a good choice.
If he says no, my sense is that you are right that he looks at the job and says “this isn’t what I want for myself / my family.” Personally, I commend those people as opposed to calling them stupid, scared, etc. (which I realize few people are actually calling him that).