I left my corporate job for personal reasons largely unrelated to the job per se. I certainly had my criticisms of the company, but probably needed to leave regardless.

So while you try to gather information, keep in mind that "not a good fit" could be a polite way of saying "It's none of your business and kindly butt the hell out of my private life, thank you."

Not everything that happens around you is about "you"/the company. That's not how life works.