Did he play his ass off this year? Absolutely. He was also surrounded by a great team and was playing for millions upon millions of dollars in his next deal. When he hasn't been motivated financially or on a great team he's been average at times and flat out poor at others.
Letting yourself get caught up in one single season (especially in a contract year) rather than looking at Chandler's entire body of work is exactly how some of these ridiculous contracts get handed out.