Yes, it is related to the violent confrontation between Hummels and Terzic in the week of the UCL final. Maybe because Hummels is a senior player there and really understands various things, then he criticized Terzic regarding the tactics he had prepared. hemm, this was quite exciting at that time. In fact, it is a very decisive event.
But never mind, the point is that no one wins or loses. yes, both of them left Dortmund. And now, Nuri Şahin as the new coach of Drotmund has been officially confirmed and they are getting started with several players to get in the transfer market later.
Humels had no right to question Terzic's authority, as an experienced player, he should have understood that bad authority in the team is worse than bad strategy on the field. Moreover, if Terzic was able to reach the Champions League final, even if it happened with great luck, he was able to achieve this, which means blaming him for wrong tactics or something else is wrong. As a result, Humels had to pay a big price for his actions, Dortmund lost an excellent coach, and Humels had to leave the team.
This is certainly a very unfortunate incident, they fought very hard until they reached the final. And playing against Real Madrid is not an easy thing with the club's various experiences and solidity. So, this should be a learning experience for Dortmund, both the coach and the players in the future. But this is already in progress. Both have left Dortmund, even though both are quite vital parts of the club. And Hummel left as a free agent. This is a good opportunity for Roma to get him.