I think one major aspect is that even if their leadership was 100% cynically lying about their intention to build socialism in China, they've still been a tremendously less evil superpower than any of their peers.

Here in the US, we started with white supremacist genocides and have continued that tradition up to the present. Domestically we run a perpetual military counterinsurgency campaign against our population, and internationally we drop countless bombs on countries we "aren't" at war with while we coup their elected leaders and train torturers and death squads for our puppet regimes. Western international "development" programs have been nakedly exploitative and repressive, while Chinese international development programs have instead been mutually beneficial

All of this happens in public view, and the worst allegations anyone can make up against China always both pale in comparison to what the US admits to doing and get retracted after a few months of our Reputable Journalistic Institutions lying about them