You are correct, but this is not the whole picture I feel. Yes, people with power still desire more power. But it's the same drive that fueled all the great pioneers and explorers of the world. Very few if any stopped after the first breakthrough and said: "Alright, I can stop now".

I consider this one of the great distinguishing features of the human race. For some people, enough is never enough. Yes, obsession has it's dark side, but without these people, we'd not be where we are today. The human race needed this trait to push the envelope. We needed (and for a while we'll still need) boneheaded bastards who won't take no for an answer.

Sometimes this obsession gets us dictators who ruin the lives of millions, sometimes it gets us breakthroughs that improve the lives of billions.