Also, it is NOT Dortmund's strategy to sell players. With every strong player that left they tried to keep him for at least 1 more year. They offered new deals with higher payment to Haaland, Bellingham, Sancho, and so on, so where would that make sense if they just want money. Dortmund wants success, they want to win titles.
If players want to move on for a big pay day and to a big name in European football you can't stop them. They have the power when their contract is expiring, nothing Dortmund can do.
Actually it is Dortmund's vision exactly. They don't prioritize becoming the champions in the Bundesliga. Instead they have a certain main vision that they have been maintaining for years. It is to bring young and talented players to the team for a cheap price and increase the speed of their development to make them young star players. After that they are okay to sell them for a really high amount of profit. These kind of players are using Dortmund as a steppingstone to join bigger teams.
Some of them push them to put a release clause on their contract as well though like Haaland did. This isn't good for Dortmund as they can sell them for higher amounts normally but there is nothing to do about it.
LOL, obviously you have no clue. Have you ever seen interviews with Dortmund's managers? Why would they even try to extend these player's contracts if all they are aiming for is money. They could just sell them and move on to the next "project" .
This makes no sense. Dortmund wants to win. Titles bring money, more TV money, higher sponsorship deals. That's why Bayern is rich and Dortmund isn't. They win, they earn.
Of course they would like to extend his players' contracts. In the end Dortmund would like to benefit from their talent as much as possible on one hand as well. Meanwhile these players will develop their skills more and increase their values much more. Just because their vision is to make a big profit in the future they don't just offer these players to other teams. They know already bigger teams will come to them after watching those very talented players.
After that Dortmund would like to have a sensible offer to be okay for letting those players go. They couldn't do it for Haaland because he had a release clause. So they wanted to keep him as much as possible to sign a new contract to remove or increase the value of his release clause. But it wasn't difficult for Manchester City to just buy his release clause and sign him.
But as for Bellingham they got just the kind of offer they would like and didn't resist Real Madrid too much. This kind of players just want to use Dortmund as a steppingstone and Dortmund bring them to the team knowing that.