I think their joy is not too great for Bayern Munich, as the Bundesliga championship has now become a classic. They predict that they will be champions as the new league season starts. The German league needs a little more competition, I agree, but other teams, including Borussia Dortmund, are not taking steps in this direction. If they don't want to be champions, Bayern will easily win. Even if the league is not difficult, success may be less in Europe.
I don't see any interest in becoming champions in teams like Dortmund and Leipzig in the Bundesliga. Dortmund's main business is to produce talented players and sell them at high prices to other clubs, including Bayern Munich. If the management of Leipzig and Dortmund had tried to strengthen their team by investing some money, the rule of Bayern Munich in the Bundesliga would have been somewhat lost.