I think failing to convince a player to stay is the main reason and not selling them. What if player puts a pressure and declines contract extensions? Then obviously it will be loss for Dortmund later on as the player will move out for free. I feel that Dortmund should find a good way to convince a plyer to stay as like this they are only waiting for Bayern to become inconsistent in the league and get the title for themselves. Dortmund are just not putting any effort to win the title like this .
I dont agree on that , and Dortmund putting a lot of effort in it to win the title but they doing that on a different way.
For sure they would be have the Money for getting very good players and hold good players , but for how long would this be working ?
Even they lost a lot of very good Players in the last years i think they are on right way and making every season little steps forward to catch up with Munich in league.
If Borussia Dortmund had not sold their players in the last 2 seasons, they would probably be the biggest championship candidate this year. If Bayern Munich becomes champion every year, Borussia Dortmund, which sells its best players every year, also has an impact on this. However, they somehow manage to fill the shoes of those players. Dortmund is a different team.