The reason why they sacked him was because Bayern Munich wasn't playing up to the expectations of the club board and the necessary steps they feel to tackle the issue was to actually sack him as a manager because if it comes to player, I think Bayern Munich already have all it takes when it comes to players to actually make things work so firing him and employing kompany is the next step, now it's just left for it to actually work out.
Any form.of incompetence been exhibited by AA coach could actually lead to him been sacked by almost any team, at any point in time a team feels like their coach has been very incompetent they reserve the right to get him sacked which is exactly what Bayern Munich did to their coach at some point. He was trying the best he could but then he's literally did ended up not impressing the management well enough they had to drop him at the end of the season but I believe he could do better in his new team when he gets hired and Bayern Munich's new coach gets to satisfy the needs of the management generally.