The answer is greed. Most of us can understand ordinary greed, the desire to have more than you've already got, the wish to be rich and to have fancy things. But few of us can comprehend the special type of ultra-greed that drives the oligarchs. They are NEVER satisfied. Five yachts aren't enough, if it's possible to get one that's fancier. A fleet of private jets isn't enough, if there's a chance a new one would be faster or more luxurious.
While we can, on an intellectual level, comprehend that someone might feel driven to improve upon his already excellent situation, what we can't understand is why someone who already has everything desperately wants to take the little we have away from us.
The problem with the never-satisfied, ultra-greedy oligarchs is that they don't just want a lot, they don't just want more, they want EVERYTHING. Anything you have, no matter how small, is something they don't have. They want it. This is why they don't care if we die of preventable illnesses, or starvation, or nuclear holocaust. Only if we are dead can they feel sure that we have nothing and they have everything.
As they build their doomsday bunkers, they fantasize about a world in which more than half the population is annihilated. Unfortunately for them, they need workers for a few things, so they can't quite wish for everyone but themselves to vanish.
