Indeed Dortmund is synonymous with selling star players which they do in every transfer market, even this season they have done it again by selling Bellingham to another club. One of the factors that made them like this is a financial problem because they get a lot of profit from the work they do which sells players at quite high prices to other teams. I don't think Dortmund will be able to give many surprises in every season in the Bundesliga because they are not too strong to compete with Bayern Munich.
This is dortmund's strategy.
It seems like that dortmund has a reason why it was doing the strategy to buy cheap and sell high. In my opinion if dortmund is not as rich as bayern. it can become a sense reason why dortmund was doing it. Dortmund has so many reasons to explain it.
I do believe if the management has a reason why dortmund was doing such strategy and that's pretty much the same like what already done in the past. Arsenal has not owned by rich owner.
That's why the club was doing such strategy to make sure its financial is always stable.
This is a good overview and Dortmund is making good money of these sales and use it to invest in higher salaries in order to be able to keep future players at the club for longer. Or to raise salaries for high profile players that are thinking about leaving the club. But Dortmund is still not in a position to make a 100 million transfer themselves and buy a player who is readily world class level. That sometimes hurts them because every time they have built a squad that is strong and reliable, it is almost guaranteed that at least two key players get bought out or leave the club at the end of the season.