Well you make a valid point. If we assume everyone is equally greedy, then what we're trying to solve is human greed in general. But regardless if greed is more common with those in power or not, It's still a big thorn in our shoe. It could be indeed that the opportunities to satisfy greed are greater for those in power, but it could also be that greed finds success in the system and bears an advantage to acquire power. In fact it might be a complex combination of these and much more. Figuring that out is one of the first steps to solve the problem I think.
Your second paragraph really put things in perspective though. I mean, most certainly there are good politicians. Could the problem lie with those in power who have a large influence in politics?
Well, It's not like there's nothing we can do. We could have moaned about a wide range of things we've managed to solve or improve over the years. We can extend the estimated span of existence for humanity. We are indeed, to a great extent, what we are born with. But we are also what we are exposed to. And we are also what we choose to be. It's a combination of these, at different levels. We can adapt, and in fact that is probably the most important feature of our species.