I really think the contract got in his head. When you get traded for, paying the full $21 million salary, expectations are sky high. The entire burden is on you.
Now that you get traded again, while you still make the $21 million, the team that has you is really only paying what, $5 million of it? Expectations are a lot lower, and you can relax more. It also helps when you are surrounded by aging former superstars also. Instead of a bunch of young guys that you are trying to mentor. He is probably focusing more on himself, than everyone focusing on him.