yeah I agree that that's the big question.

Interestingly, Dortmund has had a ton of injury issues, to the point that they fired their head physio last year over it. The fired physio says that his theory is that it's due to have two different surfaces at training -- apparently Tuchel wanted to have a training field with the same surface as the stadium, so the facility has two fields -- one is hybrid like the stadium, one is natural. The fired physio says his theory is that moving between the surfaces during the same session is what's causing the injuries.

I don't know if that's accurate, but their willingness to let him go now for relatively cheap could reflect not just a lack of confidence in his ability to stay healthy, but also (or maybe even moreso) a lack of confidence in their own ability to keep him healthy.