I don't follow the NBA closely, but I thought Johnson was one of the best coaches in the league. Dumping him certainly doesn't guarantee success in the future.
Another NBA coach, who is overlooked and not given his just due, is Maurice Cheeks.
Avery Johnson was the scapegoat. The guy's winning percentage was above .700! In the end, he'll be glad he's out of there b/c Cuban mortgaged the team's future to get Jason Kidd (players and two #1 draft picks). The team is old and is built around Nowitski, who some think can never get the team over the hump.
