In modernity, yes, kindness denotes stability and opportunity for experimentation, but is that historically the case? Sincere question, I only remember the funny parts of history.
To answer this, one would have to define what "lasts" means. None of them exists as an empire any more. So if lasts=forever it was historycally the case they couldn't do it.
They can, the real issue in ww2 was mostly that the US appeared. During the entire war, their economy was bigger than everyone else’s combined, so whatever their course of action was it would be defining