Mostly I'd say their downfall was that they encouraged copypasta material and actively discouraged any kind of behaviour that would have built a community.
I might even find an upside in that if it wasn't for the fact that this stolen crowd sourced knowledge will be used to make some billionaires even richer.
Usually the most superficial, not that it's always a bad thing.
Oh, also on SO there's this kind of exchange:
Q: "I want to do X because of this and that - or because I simply fucking want to".
A: You should never do X, do Y or Z instead.