Good news, I actually
do know everyone who was part of the original build of Wasabi! None of them left because of the language. I think this accounts for everyone who was there at the time:
1. Original author left because his wife was going to medical school out-of-country and Fog Creek didn't allow remote work at the time.
2. Second author left because his wife was going to medical school out-of-state and Fog Creek didn't allow remote work at the time (see a pattern?). Later came back because Fog Creek offered remote work. Went on to author the blog post we're talking about.
3. Developer left to go work on Stack Exchange (me!)
4. Developer left to go make the world a better place at Khan Academy
5. 2x developer left to go work on Trello
I think that was all of us. People move on in the course of 5+ years. Turns out most of those reasons don't have to do with programming language.
FWIW, I think Wasabi was a bad decision and I'm not going to defend it. But I really don't like these massive assumptions about people's motivations for leaving.