I thought from early on in the season that something was wrong with the squad, but I suppose with that feel good factor of some big transfers and also a tough start in the league that no one expected much of it masked over the fact that he had lost the dressing room. Probably many small things have built up and into the players not giving their all under Koeman.
Was the Barkley situation the start of the downfall? That would kind of fit in the timeline. If someone is well liked in the dressing room and someone pissed them off why would it not effect the other players, then maybe some of Koeman's other shall we say quirks start to niggle then before you know it everyone thinks the boss is a wanker.