First one: rare-to-unique domain knowledge useful to that team. (So, yeah, luck.) Second: founder (went nowhere, as so many do). Third: ditto. Current: Found

First one: rare-to-unique domain knowledge useful to that team. (So, yeah, luck.) Second: founder (went nowhere, as so many do). Third: ditto. Current: Founder is a long time colleague and friend from the first one, plus rare domain knowledge, plus demonstrated enthusiasm for the work while contracting with the team. So a mix of luck and hard work.