It's not that CEOs just happened to be evil. It's a material conditions problem. Anyone who becomes a CEO has tremendous pressure to become evil. You could even argue that the steps you would have to take to become a CEO are morally problematic. So the pressure to become evil starts early. As soon as you enter the job market.
Yes, but the difference is with politics things are more transparent and we have a choice. We can vote. With CEOs, we don't get a choice and no one really knows what goes on up there.
If everybody acts collectively in their own interest, we all win.
I mean this is only really true so long as everyone is allowed to vote, which is inevitably never the case. We always have certain subsects of the population which aren't really given access to democracy. It's very easy to, even in a "total democracy", still have a ton of xenophobia and imperialism, because obviously, people who aren't citizens can't vote. That's a very large top-down example, right, but this creation of subsects happens at every level. Famous more american examples are gerrymandering and the electoral college.