May be the reason why they do sell those players is because they do it as precautionary approach not to have financial problems, most team initiated survival techniques and that has been keeping them in the business of football but I don't think doing this consistently make any sense because this will get the fans pissed, it is a good idea for any organisation or club to plan financially but it also has to to be balanced, do you say make up for the trophy they weren't able to win? How possible could that be, they should come up with other strategies too, they need trophies, the need to improve their games to achieve that, so they don't have to rely on one strategy, if Guirassy prove them wrong, they may not have any option than to keep him
Maybe Dortmund do not need trophies. And they do not even compete for the title. Dortmund won the Bundesliga twice in a row in the 2010 -11 and 2011- 12 seasons. And then they didn't win another title in the 13 years that followed. Dortmund sold their best player every season. And that's why they can't compete for the title. Their only target is probably to qualify for the Champions League by finishing in the top 4 of the points table. We will see the same thing happen again next season.
What I just have to say about this is that, maybe that's what the club management but it sounds and looks very absurd, selling of their players is the business now as we can see, how will a club be comfortable with only qualifying for champions League alone by just maintaining the top in their league without sliding of the position every season just because they want be in the champions League, they might have a financial advisor that brought this idea of being comfortable with selling their stars every season lol, will this pattern help, a club that has not won trophy for those number of years and still doing nothing to win, if thats there choice then we have no say.