Avery was his own worst enemy in Dallas. His head got so big with the early success and he also didn't draw up very good set plays from timeouts, etc. It's not like Avery inherited a bad club either. He inherited a winner and then guided them to the biggest collapse in NBA history and the first #1 seed to ever get beaten by an 8. I bought into the Avery hype at first; but I think the players finally turned on him and he had NO control of Josh Howard.
As far as Calipari I heard him speak at a coaches convention a few years ago after being fired by the Nets; he was super bitter and made lots of sarcastic remarks about how "he forgot how to coach" when he was in the NBA. I don't think he'll jump back into that.