First of all, there are no more rich clubs like Bayern Munich in the Bundesliga. Secondly, neither team probably wants to compete with Bayern Munich for the title. The Dortmund team is quite strong. Had Dortmund not sold their best players every season they could have built a squad capable of competing for the title with Bayern Munich. But they don't. And this is why we see only Bayern Munich's dominance in the Bundesliga every season. Next season we will see the dominance of Munich.
There is another interesting situation. Borussia Dortmund sold many of their important players directly to Bayern Munich in the past. This was a huge strategic mistake. With this strategic mistake, Borussia Dortmund lost the possibility of approaching the level of Bayern Munich. Of course, not everything is finished. If Borussia Dortmund had managed to be a little more careful last season, they could have destroyed Bayern Munich's hegemony. Frankly, I think Bayern Munich will dominate the league next season as well. But football is a game of surprises and maybe we can watch a surprise.
In essence, Dortmund will always be willing to sell all their key players to clubs that have money and are willing to pay. So, even though Dortmund sold their key players to Bayern Munich, basically it was like a tradition to be done by Dortmund for a long time. But the great thing about Dortmund is, even though Dortmund always sells their key players every season, but every season Dortmund also always manages to be Bayern Munich's competitor at the top. Also, in the second point you said about "no team wants to compete with Bayern Munich". I don't think that's right because after all, every team is always trying to stop Bayern Munich's hegemony but yes, because Bayern Munich has good consistency it is certainly difficult for other teams to be able to compete consistently with Bayern Munich.