A graph of birth rate by income level shows us the simple truth: lower income people have more babies.
This means that as a society prospers and adopts hygiene, organization, nutrition, and other necessary elements, it gradually drowns itself in impoverished people and has to find jobs for them all, which in turn creates a vast establishment based around low-skilled labor.
At some point, the people doing the low-skilled labor notice that they are not earning very much; replaceable people, especially those who are not very reliable, tend to get paid very little. In Communist societies, they are effectively treated as disposable.
When the low-paid and low-skilled contemplate this problem, they conclude that they do all the work and therefore are most valuable, because they biologically/genetically cannot understand the role that leadership and institutions play in the ability for society to maintain itself.
These low-income people represent the ultimate in bourgeois thinking, which holds that maintaining civilization is a job for someone else, and all that matters is the profit to the individual. In saner times we know this as “individualism.”
They promptly stage class warfare, overthrow their leaders, and elect those who pander to their (limited) beliefs. This invokes a stage of dysfunction, and the society declines into third world status through “solutions” like socialism and diversity.