It is not easy to dominate the Champions League and become champions in a row, and when Real Madrid managed to win the title 3 times in a row, they got it in a way that was not easy at all. Real Madrid's advantage when they did that was that their players had a very good winning mentality, so they were able to do something that had long been considered the "curse" of the Champions League.
At that time, Real Madrid had a luxurious squad and almost all of the mainstay players were players who had captain status in their respective countries. That is another advantage they have so that they achieve enormous success.
Next season they are also believed to be able to defend the title, but this is the Champions League and everything will be more difficult to achieve.
In the champions league, nothing is easy to come by and for Real Madrid to win the title three times in a row, it was such a tough fight for them and they hard to put in all their efforts and give in their all to have achieved that three times consecutively. I am sure they were not expecting to have won it in a row like that, but with their unrelenting effort, they became victorious again and again. This is not even about players having captaincy status in their different countries, they were just in their best form as a team and no any other team in Europe can stand them at that moment.
As for Bayern Munich, it is impossible for that to happen next season in the sense that they just changed their coach and brought Kompany who I don't think will be able to add much impact on the club's performance next season. He should focus more on how to win Bundesliga and not UCL because much is expected from in from the fans.
I won’t belittle Kompany to the extent of what he can achieve because I won’t conclude on his managerial skill on Bayern Munich when he’s yet to manage them for even a season. He might have fumble while coaching other low tier teams but I don’t expect him to do the same in Bayern Munich when he has the full squad and every support he’ll need to make the club better and prosperous in the league fight and also in the UCL.