Since wealth attracts more wealth, and power attracts more power, in any capitalist system, without constant redistribution of wealth to the bottom, eventually

Since wealth attracts more wealth, and power attracts more power, in any capitalist system, without constant redistribution of wealth to the bottom, eventually you wind up in a situation where a tiny group of people at the top have all the wealth and power. It’s a basic feature of any society where property can be used to make money. UBI would appear to be a pretty straightforward way to keep things balanced and stable, in the long term.