Why is it that so many decent companies ends up being sold to private equity? Is it a reality of the economics, do people get greedy, do people get burned out?

Private equity almost always ruins a company, normally the culture first and the product thereafter. I can't imagine the creators being completely ignorant or feeling good about that?

Maybe, just maybe, founders sometimes need a way out. Maybe they've given enough of their life, they just want to cash in, and they decide to put up with the downsides (which they almost certainly know about).

Disclaimer: I have never founded a company, so I'm just guessing at what the motivations could be.