The man has presided over three labor stoppages in less than 20 years, that is unprecedented. Also, he is virtually the only common link between the three. It was well documented during this latest dispute that there was little effort to negotiate at all on the part of the owners and Bettman until after they started cancelling games. A move that doesn't show a shred of respect for the fans of the sport.
From everything that I have read, it is due to the direct action of Gary Bettman that the lockout happened in the first place. For whatever reason, he did not want to compromise with the owners and the players in any meaningful way. Of course this would lead to a lock out.
The bottom line is this fell apart because of Bettman. The owners and the players had enough trouble as it was but Bettman has made it clear that he does not like the players or the players labor union, and he was going to do anything to destroy it. Bettmans one sided view only cost hockey fans.
A good amount of the blame for the NHL lockout falls on Gary Bettman's shoulders. He is a terrible GM and the worse one the NHL has had. The league has gone downhill since he took the job. It seems like he is in cahoots with the owners and does not like the players or the player's union.