I left because I never had interest in staying in Michigan in the first place, though Ann Arbor is absolutely gorgeous and if I wanted to live outside a major city it would be one of my first choices.

Salary is one part of that, but unless you grew up in the area, most non-hub-city regions are a hard sell for young folk, and Detroit hasn't yet recovered enough to be "hip". People used to have for move specifically to find a job, but in tech there are so many jobs available currently that you kind of get your choice of destination if you're a capable engineer, especially with remote work available.