I think Holding just kinda gave up on being a footballer. He got his new fancy hair, and then a model girlfriend, and since his early 20s he's been richer than any of us will ever be. When you're not that talented (comparatively) these things can end a career prematurely.
He was probably decent enough to stay with us as a 4th choice CB, but I doubt Arteta would have allowed that kind of open lack of ambition if that makes sense. He wants players fighting to start, not someone who has accepted they're never going to be more than a squaddie at the age of 25.
