I had always thought that the Chinese were (largely) Buddhist. I’m confused actually how much atheism was promoted in one communist nation versus another. Not really knowing the history of every communist (or former communist) country I wonder if perhaps a “policy” of kind of looking the other way on religion — while the state was nominally atheist, may have been what actually occurred in a lot of countries.
I happened to just be looking up the numbers of followers of religions in the world; and there seems to be some variation between sources. A major religion of the world, though, seems to be the Chinese folk religion. Maybe syncretism is very common in China, I believe that in Japan it is not really any issue at all, it is quite commonplace in fact, for one to be both Buddhist and Shinto.
Wikipedia has 750 million-1 Billion followers of the Chinese folk religion in total. The CIA World Factbook has Buddhist 18.2%, Christian 5.1%, Muslim 1.8%, folk religion 21.9%, Hindu < .1%, Jewish < .1%, other 0.7% (includes Daoist [Taoist]), unaffiliated 52.2%, and officially atheist as the religions/religious beliefs in China.