We all suspect Borussia Dortmund is focused on selling players. They've been saying this for years. Furthermore, many world-class star players have played for Borussia Dortmund. Lewandowski and Bellingham are prime examples. If they wanted to compete with Bayern Munich, they would do it. But I think the team's priority is making money.
One player you haven't mentioned is Haaland, who was once part of Dortmund and has since become even more successful, with his talent widely recognized in the EPL.
And when you think about it, if Dortmund's main objective is to make money, winning the bundesliga could also bring financial benefits. On top of that, if the club kept its best players, they could pursue additional rewards in prestigious competitions like the UCL. Unfortunately, Dortmund seem to prefer the immediate profits that come from selling their players.