One of Borussia Dortmund's characteristics is that they train the players they buy well. They identify especially young and potential players and sell them to important teams in Europe after they have been trained well. There are many examples of this, but the latest example is Jude Bellingham. Beier currently has this potential. Since they transferred him at the age of 21, they can sell him to a big team again in a few years for a very high transfer fee. Borussia Dortmund does this job very well.
Borussia Dortmund is one of the best clubs that can bring in potential young players and they can make them into players with very good performance. Previously they found Haaland who now plays at Manchester City and became a goal machine there, then they created Jude Bellingham who is now a mainstay player at Real Madrid. but they use the player only to gain profit, not to achieve achievements.
Borussia Dortmund's talent scouts are very observant in seeing the potential of a player, and not just the 2 names I mentioned, but if we go back to the past then there have been so many players born from them, including players who are mainstays of Bayern Munich who in the Bundesliga are their main rivals. That is their expertise, but unfortunately they do not use the expertise they have to achieve an achievement and become the best club at least in the Bundesliga.