Second is that we are by nature social animals. We work together, we collaborate, we are more efficient when we share resources. Marx's criticism of capitalism is that capitalism replaces this egalitarian collaboration with conflict, and that means that it isn't a natural system after all. And by arguing that capitalism actually isn't consistent with human nature, Marx sought to empower the workers. That's a lot more attractive than Blanqui's elitist socialism, and while purportedly Marxist states like the USSR usually abandon worker empowerment pretty quickly, the idea of protecting our collective interest remains powerful. That's where we'll leave it for now, lest I start reading from the Communist Manifesto. But ultimately, socialism has not succeeded in supplanting capitalism, as its proponents had hoped.