I think the money aspect might have been the decisive factor here for that transfer. Maybe there was even a deal with the league in the background that Barcelona promised to let certain or several go in exchange for the license for Lewandwoski and the other guys. For Tuchel the transfer is a good one. I expect Aubameyang to play in a central offensive position and that is what Tuchel is currently lacking.
Bottom line is though that I believe Barcelona would have kept Auba if they had the money.
it also makes sense. but when Barcelona already has Lewandowski in attack, I think Aubameyang will be on the bench more often.
This transfer will give Aubameyang a better place and playing time in the first squad. he's a good player and is doing pretty well at Barca. this is an opportunity for him to show his better qualities with a new team. good luck to him.