Dortmund's goal is to buy more and more young players and earn money from selling these players and that's their first priority otherwise they could keep the superstar palyer they had before.
Also, I think Dortmund is a great player supplier for Bayern Munich and there are many players from Dortmund who left this team for Bayern Munich because Dortmund could earn a good amount of money.
Looks easy right? Looking for young players and after developing into better players sell them to gain financial profit, but actually, it is not as easy as imagined because these young players have to be in a good club atmosphere as well as good competition so that their skills improve and they can become better players, and Dortmund is a club that has this, so many young players can become better when they are in that team, it's just that Dortmund never intends to keep these players, maybe when there is a change in management so the club's way of continuing to earn money will be different and no longer focus only on selling potential players, because fans will be very bored with things like that and they also hope that their favorite team can become champions, not just good competitors but always fail to lift the trophy like previous seasons.