He was dropped for having an attitude. Same attitude that got him benched at City by Pep.
The truth is Sane was a young talent with potential (I.e. a Palmer type player) who acted like he was Ronaldo (i.e. the Super super team star), and he did this everywhere. At his National team and here at City.
Pep and the German coach correctly benched him. And he wasn't picked for the national team coz his attitude wasn't right
By the way, at the time he wasn't necessarily better than the players picked. He was just different (i.e a speedster and they didn't have any other options on the squad). So it would have been wise to take him. But his attitude stunk. And the manager wasn't having any of it. Neither was Pep. And I agreed with Pep at the time. So have no reason to doubt the German Manager
None of this has any relationship to playing in Germany. The starting midfield at the time (Kroos - Gundogan) both played outside of Germany, no one cared.
I'm okay with Sane and would have him back as a back up. But he wasn't bullied by anyone. You couldn't bully a young Sane if you tried. He was arrogant, self assured, moody and headstrong.
Everything he did, he wanted to do. Even the claims of his Mom pressuring him are probably overblown. Knowing his personality, he probably said he wanted to go be the star at Bayern rather than conform to this tyrant's (Pep's) rules. And his mom was simply co-signing his wishes.
No one bullied Sane. No one.
