It's an issue of individuals: People are neither completely altruistic nor completely greedy. A very important factor is, where are the elite on that continuum? My humble hypothesis is that that's the main difference between a banana republic and first-world civilization and society. IMHO, the elite in the U.S. have swung far toward greed; the tax bill is a good example: There is no policy reason for it, not even a figleaf discussion of economics, and even the principles of conservatives (deficit reduction) are thrown by the wayside: They just want more money.

It's also an issue of systems: How do we design a system that marries power, on one hand, to justice and welfare on the other? Then those who seek power also seek justice & welfare, intentionally or not. Democracy is an (incomplete) solution to that problem: Power flows from making the people happy.

Despite the problems, the U.S. and other major democracies work and have worked for generations, and they work better than any other system of government. Somehow, I'm not sure how, that happens.