Maybe Kingsbury looked around the league at the crappy HC positions available and just said "Aw, Phuket!"
Same reason Jim Harbaugh is going back to Michigan. People hype up the Denver job for some reason, but they have little draft capital and if Wilson is washed, you're stuck with him for years. In a tough division, no less. Colts have a crazy owner. Cardinals are circling the drain and Kyler Murray is a problem, not a solution. Just not a lot of good positions open and I think it's much less this year overall than normally.
Now, if the Chargers fire their idiot Head Coach for getting Mike William and Bosa hurt in a meaningless Week 18 game and then choking away a 27-0 lead, that would be a good job opening.