I don't really know why many people think that Bayern Munich's performances will decline or will not improve under Kompany as head coach next season. Kompany is not that experienced as a coach, but that shouldn't mean we judge him negatively. It would be better to allow the season to start and see their performances before rating Kompany as a poor coach. As for me, I believe that Bayern Munich will surely be in the race for winning the Bundesliga trophy next season. Bayern Munich will be a great challenge for Leverkusen, not to mention Dortmund. In fact, from my observation, I can't say if Dortmund will even be a good contender for next season's Bundesliga trophy, but let's see what happens.
People are being judgmental on Kompany because he has no good record in the past career that will make them believe that he can revive Bayern Munich from their current form. Kompany was poor in his last management as a coach in Burnley and even made them finish as a relegated team. Even with out a doubt, that is one of the major reasons they don’t see him as the best coach for a big team like Bayern Munich.
This is football and anything can happen. With the quality of players they have in their squad now, I don’t think Kompany will be that poor in managing the team. If he can’t do better than the previous coach, I don’t think he will do worse than him. His approach to matches matters a lot and how he organizes the team to play will play a significant role in making them successful next season.