First time i hear the german league being called tactically superior. German league is the least tactical of the top 4.
As for the players, again, culture. When foreign players move to a foreign league, they will have to adapt to that league. In England, that means less thinking, more running. Keep in mind, the very best teams don't always adapt to the league, as they have enough quality to force the other teams to adapt to them. Mourinho's first chelsea didn't play in the high-tempo, all-out attack typical of the premier league. Neither does Guardiola's city. These are just two examples.
Having said that, Diego Costa's goal was just shocking. As if the entire City team switched their brains off
Conte did what he had to do with the limited options at his disposal. But the whole point of sitting deep is to prevent your opponent from creating many clear cut chances to score, while using counter attacks to create a few clear cut chanves of your own. Chelsea failed in preventing city from creating chances. They were succesfull in creating great chances on the counter. Only half of their tactical plan worked. Hence they didn't win the tactical battle. They were simply more clinical in taking converting their chances.
They also won the mental battle. Never left the game even after city went up and looked poised to close the game. City on the other hand folded after Willian's goal