I think I said this before, but they didn't lose the title in the last match at home, they lost the title in a dozen of matches they should have won or tied before the last match was played. Dortmund is just not good enough and it has been like that for a while now. They have good weeks and then it looks as if they were able to break Bayern's dominance, but then the disappointment is so huge that nobody can trust their eyes what's happening. The last game last season was only the tip of the iceberg. The whole drama enfolded over the course of the whole season.
If the match does not end in a draw then the Bundesliga title will belong to Dortmund and it hurts because it happened in the last match at home. Dortmund have talented young players but they are just trying to make a profit by selling them and there is nothing wrong when the club tries to play a game like this but they don't need to talk about fighting for the title. I don't like the style of club management that seeks profit in this way because it can't provide anything good for the club.
Currently, conditions are increasingly changing where in the league another strongest competitor has emerged, such as Leverkusen and perhaps Dortmund's position will become more difficult because so far the match has taken place, they have only been able to collect 27 points from 16 matches. Dortmund's focus may no longer be on challenging for the title and what they need to do is how to qualify for the Champions League next season.
You are forgetting the fact that Dortmund is a publicly listed company and that makes management decisions harder to justify in front of shareholders. If they receive these big offers from big clubs that want to buy talents for a lot of money, it is risky for the management to say no. Often times these players have release clauses like Haaland or the contracts are about to expire one year later and Dortmund has no choice but to sell them. Dortmund is not attractive enough for these players to accept a higher salary and stay longer with Dortmund. Just take Bellingham as an example. If Dortmund offered him 25 million net per year, he would still have left to go to Real Madrid and frankly, he would have made the right decision as we can now see. Players use Dortmund as an interim stop in their career.