You must look at it from his point of view. He still thinks that he has something to offer in the greatest league in the world. He knows London and was very well settled there, so it must have been a big factor for him to join a London-based club. At least he turned down Liverpool's approach. But I believe that, in his heart, he is all Chelsea when it comes to English football.
And since it would be a London club in the Premier league, it would be very hard to choose which team to join, since Chelsea have not shown any interest, without alienating his Chelsea fans. And it has come down to two bad, bad choices. He must think, would he like to join a relegation battle with WHam or a battle for a Championship League spot with the Sp**s. From a footballer's point of view, who thinks he has something to prove, it must be joining the N17 scum.
I, for one, am still a fan of his and wish him all the luck, wherever it may be. (When he's not playing us!)