Not unusual for players to come from the Bundesliga and struggle.
Sancho, Werner, Havertz, Pulisic, Haller etc. Leon Bailey found his level at Aston Villa.
I feel like its more uncommon for top bundesliga players to hit the ground running in the Prem. They just aren't really at that level. City signings are a bit of an exception (Guno, Kdb, Sane).
Makes sense to have a lot of them a tier below!