It's not correct to think that capitalism is some natural force. We form states to decide on the rules of the game. The fact that some of the rules are made by people like buffet in conversations with public officials and lobbyists is where the whole 'this system was designed' thing comes from.

Billionaires and millionaires speak with presidents all the time and develop strategies publicly with them, it's foolish to think this has no effect on the structure of the capitalistic system at all.