Put simply, Phelps has made it clear through his actions after Beijing, that he is not motivated to dominate at his sport.
Phelps nearly failing to qualify in the 400 IM shows he just isn't in the condition he needs to be to bring home golds....he looked so bad I wouldn't be surprised if he wins just 1 or 2 golds (which is honestly how tragic this is, because some people train their whole lives just to win 1 and Phelps is squandering his abilities to win them all).
Also, I feel like Phelps is trying to act like he doesn't care about winning unless it's a relay/team event. To me it's like he's battling his own demons that his celebrity has brought.
Phelps looks like a rock star who is tired of singing his hit song after 10 years of singing it, but is forced to because he's under contract.