The fact that they are just doing good in making money through those buying - developing - then selling it at super high prices .,, having those domestic league success will always become second priority as they have set the priority at the first place , no wonder if by then dortmund will only get a trophy once in 10 years , sad fact but profitable.
Pure business? Idk , winning bundesliga earn you €80m ... but dortmund earned more than that without winning anything.
Indeed Dortmund is synonymous with selling star players which they do in every transfer market, even this season they have done it again by selling Bellingham to another club. One of the factors that made them like this is a financial problem because they get a lot of profit from the work they do which sells players at quite high prices to other teams. I don't think Dortmund will be able to give many surprises in every season in the Bundesliga because they are not too strong to compete with Bayern Munich.