As coach, you can't have your most prominent players as enemies. In my life, I've learned a saying: the enemy in your own bed is the most dangerous. That's why we had to act.
The surprising lineup that Ancelotti announced without commentary prior to the game against Paris Saint-Germain considerably deepened the discontent in the team. As Hoeness summarized,
The fact that, in my view, in the past few days the coach turned five important players against him - Coman, too, whom he also didn't let play - at a stroke, he never would have made it.
The list of players irritated by Ancelotti’s tactics would thus seem to comprise those left on the bench Wednesday - Arjen Robben, Franck Ribery, Jerome Boateng, and Mats Hummels - Kingsley Coman, and potentially another player (Thomas Müller springs first to mind).
With virtually half the team opposed to their coach, Hoeness and CEO Karl-Heinz Rummenigge decided immediate action was necessary. As Hoeness revealed, the decision to dismiss Ancelotti was made around 3:30 AM today.
If you lose the locker room, you lose your job.