Maybe that's what the player wanted. I think this decision was made in a centralised way, the management discussed it with the player himself and stood on his side without interfering. In fact, if it really was like that, it is a very favourable departure from the club. What's more, he will be no worse off at barcelona, staying at the same level
Apart from being very profitable for the club, Gundogan himself also has nothing to lose by leaving for a big club like Barcelona because he didn't go to a bad club. Gundogan can still have a very good career at Barcelona at a level that is not much different from before so that Barcelona will also benefit enough to have Gundogan next season. Because that will make Barcelona stronger to compete with other English teams when they meet in the UCL competition.
I agree with you. He is a very good midfielder, he has relatively good stats and what's more, he was a bargain for Barcelona. Such a free reinforcement (not including wages) is incredibly good, so hopefully he can fulfil himself in Spain as well. Nevertheless, I think they are still weak for the Champions League