Or, he "knows his level." On the best teams in the world, he will likely be the second keeper. "It is what it is."
He has zero caps at any level for Germany. He is a good GK but not a great GK. If he wants to be the the number one again, he may have to do it at a mid table or lower side in the Prem or move to France, Holland, etc to play for a "big team."
It's no shame on him. He's miles better than any of us ever were or ever will be as a GK. The lure of £ is powerful though. It's probably been difficult to leave being the number two here knowing he may not make as much money elsewhere.