There’s also the “lying flat” phenomenon, where their young people have lost interest in striving for the glory of the Party.
https://www.thedailybeast.com/how-lying-flat-took-chinas-overworked-millennials-by-storm
My personal suspicion is that China’s system requires so much intense work by men in order to qualify for getting a wife, that men choose to say “screw it”, do the minimum, relax, and have a life.
In addition, single young men in China who are only children have the prospect of caring for aging parents without Social Security or Medicare.