I had the same question at the same time but was unhappy with the Marxist answer. Indeed, it doesn't provide any explanation on the cause of the class divide in the first place. Then I noticed that billionaires had above-average IQs while reading "The Hard Thing About Hard Things" and have since dived into genetics.

Conclusion: Socio-economic inequalities are a matter of biology, not economics.

But it's very difficult to explain without getting banned or attracting a ton of bad press.