Vincent Kompany is not a mistake, Bayern Munich will push better for brilliant results and they've become one of the top clubs to withstand pressure. Believe me when I say, Bayern Munich will fire for excellent results and they're the best in Germany. Bayern Munich have come to the standards of elevating their club so appointing Vincent Kompany was probably the right choice for the club it's all clear when they're desperate for winning.
But the fact that they signed Vincent Kompany after receiving refusals from many other coaches (if I’m not mistaken, we are talking about 9) raises certain suspicions. I'm not saying he's good/bad (I don't have an opinion on him yet) but he certainly wasn't their first priority when they were looking for a coach. It is all the more surprising that the contract with him is quite long-term, but apparently there are clauses (about results) that allow it to be terminated early.