First I'll admit this is not my area of expertise.

China killed millions of people through deliberate famine campaigns and bad public policy, but it was more effective at isolating Chinese people from Western ideas. Eventually, when this isolation became untenable, China's government kept the title of "Communist" for its ruling party but quickly dismantled any policy that had exhibited anything like communist ideas. A focus on transforming the economy replaced the superficial exultation of the hardworking peasant that had been the norm since the Cultural Revolution. Remember Tiananmen Square? That was what happened when Chinese people first started being exposed to American ideas directly. The government was successful at continuing to suppress these ideas for longer, probably mostly because they were geographically isolated from the West.

Eastern Europe was always more of a focus for subversive activities and espionage from outsiders, because it's really, really hard for a white CIA agent to avoid notice in 1980's China. Because China's economy didn't have the diversity of the USSR's (read: people were poor), there was no angry middle class clamoring for sitcoms and Velvet Underground records. The USSR thought the American TV show Dallas would be safe because the villain was a wealthy capitalist, but it became one of the cultural artifacts that introduced the masses to the simple luxuries that Americans took for granted.

In short, China didn't follow the same trajectory in terms of its introduction to American ideas. By the time most Chinese people were exposed to American luxury, the government had already recognized them as aspirational and modified the economy in response.

As for "why communism", I can give a brief overview of my understanding of Marxist thought. Marx started from the premise that all value comes from labor. A person does not provide value by allowing use of their land, or of gold. Wealth and comfort acquired by access to materials is undeserved. When you see a handwoven silk tablecloth, that tablecloth is not valuable because silkworms are valuable, but because a human can make only a limited number of such artifacts in their life.

So start from this premise -- that labor is the source of all value -- and then look at the state of things during the Industrial Revolution. People were losing their livelihood and entering inferior arrangements. Artisans were losing value. Marx believed that human history started with people freely committing to creative work, but that work had been dehumanised by the rule of the wealthy and powerful. Workers were increasingly productive but only suffered as a result of it because their labor was dehumanized and they would never experience its fruits, so they were deprived of any purpose in their work. Marx considered such a system unconscionable and unsustainable.