He's not playing bad, he's just not infallible. He's still more consistent than probably any other top player save for maybe Infiltration right now. It also doesn't help that he's been playing Ryu since 2009, a character who is pretty unremarkable. He's still the number 1 player and as such he has a big target on his back. With the advent of youtube and the resurgence of fighting games, everyone is studying his play. If everyone is watching you intently, I'd imagine it would be that much harder to stay at the top, which he's still managed to do.