I'm sure Bayern can still put in another different performance in the Community League and it will be easy to beat them.
I don't understand what are you trying to explain, but it is not Community League. It is the UEFA Champions League, this is the highest football competition in the world. No team has a guarantee to win UCL trophy, including Bayern Munich. In the quarter-final, Bayern Munich will face Arsenal, it shouldn't be easy for Bayern Munich to beat Arsenal. If you look at the EPL standings, you must be aware that Arsenal is strong enough to challenge Bayern Munich.
You are right that no club is certain to win the UEFA Champions League trophy because of how competitive the UEFA Champions League is. It might even turn out that Real Madrid, Bayern Munich, and Manchester City, who are favorites to win this season's UEFA Champions League trophy, will not win it. That is why it is called the UEFA Champions League.