From what I heard, and what has happened nationally, P5 programs and top mid-majors want to hire women, especially women of color. Campbell does not fit either, and though he interviewed at UW (I believe), I've heard he was never seriously considered.
I don't know, of course, but it seems like he realized that if he wanted to be a head coach, it wasn't going to be at a top-level school. The expectations are low at Sac State, I believe it's easy to get into, and his West Coast recruiting connections will still pay off -- but now, instead of club coaches helping him get future WNBA kids at Oregon, they'll help him get players who are a little overqualified for Sac State. And that could be enough to win a lot games, and get a "better" job.
Also, he may have gotten some promises about facilities, staff budget and recruiting budget that makes it more attractive than it appears.