The obvious guess is that they've probably been monitoring him, but were wary of his reputation for falling out with teammates/managers/etc and generally being a disruptive influence off the pitch. Can also see quite a few managers not willing to take a chance on a flair player who might not buy into the team ethos or might not follow tactical instructions.
Similar to how Anelka ended up at Bolton, then a season and a half later had ManU and Chelsea scambling to sign him (even though he was the same quality player ability-wise he has been for much of his career and prior to his move to Bolton). It probably just needed someone else to take the risk and show that he wasn't an unsettling influence and his ability did warrant investment.
I reckon this is spot on.