Hmmm - I'm always dubious about these claims that we or other teams lack leadership or are not mentally strong enough etc etc
That certainly wasn't the case when we were winning trophies under Wenger with Vieira, Henry, Bobby, Campbell, Gilberto etc etc. I think what he really means is that we weren't good enough anymore. If your players are good enough you'll win games and be given credit for leadership, fight, mental strength etc etc etc
Wenger didn't magically lose the ability to develop these traits in his players or to pick those that had them and not pick those that did not. He lost the ability to find players who were good enough.