From the chats I had with folks in China they said these massive developments got promoted to people as investments. So people put their savings into them thinking they’d pay off. Turned out these new units were far too expensive for the vast majority of Chinese people to afford so they remained empty. It is going to be a mess. I wouldn’t be surprised if the gov just stepped in and seized the properties and rented/sold them out at lower prices just to prevent a collapse and put them to use.