If they were rational people they'd likely have stopped their quest after the first few millions. They are driven by pure greed and their humongous egos, none of them is sane.
They are all psychopaths, devoid of normal human emotions.
Some of the behaviour stems from their situation itself.
The huge difference here is that for these billionaires, everybody else is a "far away consequence". It's as if I kept tossing my garbage into my direct neighbor's window and flushing my toilet into their kitchen sink.
They are far safer people compared to those who dont care about virtual wealth numbers.