This is Borussia Dortmund's business style, this club can be said to rely on buying and selling players and so on every season. we can even review, almost every season they produce talented young players. Over the years, Dortmund has always been known as a pretty ideal club. they are able to excel and play attractive football as well as earn income from selling players without disturbing the solidity of the locker room.
Uniquely, the player's departure did not interfere with the team's material, in fact, Dotmund still finished in the top 4 of the Bundesliga regardless of his coach. currently, only Bellingham they released to Madrid. we don't know if other players will follow in Bellingham's footsteps. or, Dortmund will still hold it for the next season. at least, there is still Adeyemi, Youssoufa Maukoko, who has the potential to leave or be retained. in essence, Dormund had gained a huge advantage just letting Bellingham go. plus, their target is still achieved to finish in the top 4 of the Bundesliga. so, don't expect big if Dormund wins the Bundesliga trophy.
basically, if the Bundesliga wants to be like other leagues they have to change the 50+1 rule.
Over the years, we've seen Borussia Dortmund sell their most prized players to not just non German clubs but also to their major rival Bayern Munich and that's been their biggest problem and has also stopped them from winning the German league or doing well I Europe.
I think it's something that's very acceptable to the club's management as it been fetching them real gains. I think Bayern Munich are more taking advantage of the policy because it does make Borussia Dortmund less of a serious contender when compared to them
We can see Dortmund's history, they had triumphed in the early 2000s. however, it was hit by a financial crisis that nearly bankrupted the club in 2005. At the same time, Bayern Munich, as their rival, helped by providing loan funds. in short, Dortmund changed their business style. because, to overcome the club's finances must change its business strategy. and yep, as we see today. Dormund is a club that has given birth to many young talents. they are very adept at seeing young potential, to make it a star. after that, Dormund did not hesitate to let go of its players at a fantastic price. that is why, Dortmund did not target to win the Bundesliga trophy. even as you said, Dortmund did not hesitate to let go of their star players to their rivals. Basically, business is business. at least referring to some of the sources that I read, the German league ticket prices are the cheapest compared to other European leagues, not to mention the 50+1 rule which is burdensome while making the league not so competitive. that means, Dortmund can not only rely on ticket sales and sponsors. therefore, they are more interested in creating young stars, then releasing them at a fantastic price.