I think it's been slowly unraveling since Poch said before the CL final about leaving if they won it. How do players then have faith in the manager long term?
For a manager to come out and say his future hinged on one game, it just filters down to the players, and when they start attracting interest from elsewhere, they see it easy to leave a club that doesn't have any longterm stability, they stop playing for the club and the manager and there's no way back then.
He's gone, sooner or later and he's engineered it himself, either knowingly or he's been really really fucking naive. Kane, Eriksen and co will all be getting picked off over the next two transfer windows.