It's possible, though, that this small proportion of wealth has a disproportionate effect on the political process, and then the political process has secondary

It's possible, though, that this small proportion of wealth has a disproportionate effect on the political process, and then the political process has secondary effects on the wealth of non-billionaires. To pick an extreme and unlikely hypothesis, it could be that if there weren't any billionaires corrupting politics, then the economy would be run in a better way which enabled everyone to become millionaires.