It's not just about having a belief that their economic system is better, these people feel like they're possessed by cult like quasi-religious force, as were past ones like in the cultural revolution. It's the only way the current environment in the US makes sense because it's not logical whatsoever for this many people who grew up in Western countries to think having a revolution and replacing it with an ideology that's clearly failed is a good idea.
Why does this keep happening to human race? What is actually motivating them? Noting that these commies are insanely manipulative and dishonest therefore what they really claim to care about can all just be a front, like arguably the entire usage of race.
It's a melange. First, I believe a fair amount of posts online for bad ideas are bots and meant to sow division and push forward DS ideals. But for the people, most are just ignorant. Some believe they can live an easy life with healthcare and basic income if everyone would just get on board. Some seem to believe they would among the power brokers of the new regime and are inticed by that. Some are just genuinely massively naive about both human nature and the way the world works regarding parasitical secret societies and other forces at play. They probably actually think it would work, as society stands right now, if the RIGHT people were in charge. Many don't think too deeply about it, but feel it makes them moral, or popular, or edgy and revolutionary (depending on the target audience).