In the span of a month, two close friends left their companies. One had a buyout that couldn’t meet the company pref-stack. The other was pulling his hair out due to co-founder conflict and needed to quit. They're both still having a bit of a tough time. When I left my first company, I left on pretty good terms, and I also had a pretty rough time.
There aren't a lot of great resources about how to get through that period immediately after a founder leaves, so I wrote up some notes on what helped me in case its helpful for other people