Bates is just doing what any politician does, which is saying what he thinks will get him the most votes. During the CMS project approval/lawsuit he got the feeling that his voter base was largely against it, so he was too. Now that the construction is done and people have nothing to protest against, he can go ahead and say nice things about it.
So it goes. As was predicted way back when the whole fight began, the stadium update got built and everyone is generally fine with it. Probably not worth the fight, but this is Berkeley.