Maybe the problem is that Jefferson thinks he is smarter than his agent. That would seem to fit in with his personality.
Jefferson is a big name, but the more you analyze his game, the worse he seems. I honestly don't think he's all that good of a player. He's a nice finisher around the rim, but what else? His defense has slipped in recent years, his head doesn't always seem to be in the game when I watch him, he's an average shooter, he seems most happy when he gets a lot of shot attempts.
I really think Josh Howard might be more useful, at a fraction of the price.