Elders

You presumably pick elders as leaders because experience has given those of them willing to learn some perspective, an understanding of what patience means, some sense of proportion, and accumulated knowledge. Not that we have a habit of doing that in this country, but think about organizations of smaller scale than the state, and you may see instances of what I mean.

You'd also hope that habits of virtue would provide some inertia against the pulls of temptations.

Maybe they do--somewhat. But I suppose that power has its own set of temptations that most of us haven't been exposed to: to listen to sycophants, to be flattered by groupies, to come to enjoy arbitrary exercise of power. But history and literature (and, sometimes, our acquaintances) are full of the theme of a worker/conqueror who builds a fortune/dominates an empire only to have the children/grandchildren (born to power) fritter it all away. (Yes, I know I'm defining virtue a bit widely when talking about warlords, but they have to have at least some self-discipline and courage.)

I'm not sure there's a simple and robust way to survey this. If, for example, you looked at the history of family businesses, you might have some difficulty, from outside the family, in distinguishing mere lack of skill from carelessness.