Why are Chinese mostly atheists?

are far more likely to be Christian than Mainland Chinese students? A few friends and I were sat around a table during a house party. There were several Mainland Chinese present (two had been invited and the others tagged along). We asked each other questions and came to the topic of religion. I was brought up as an Anglican, but my parents hardly practised. My other white British and white European friends were a mix of Catholics, other Christians, and atheists by upbringing. Most had concluded to being personallt agnostic or atheist by their late teens. My coursemate from Saudi Arabia had been brought up Muslim and remains a Muslim. But then all the Chinese students said they were atheist, had never practised a religion and their families were basically irreligious.

I wasn't overly surprised, but then I recall the number of Malaysians/Singaporeans and Hong Kongers who are part of the university's choirs and Christian societies, and it makes me wonder - are Mainland Chinese less likely to be religious?