This crash was always on the cards. Just a matter of when, and the when may have finally arrived.
It's pretty simple.
If you believed China was going to keep growing at 10% per year indefinitely - then the property prices were a bargain.
I think you needed to be mathematically challenged to believe that, but a lot of people did, or at least thought everyone else just assumed it would happen and they could get in and out before anything bad happened.
You also have to realize it wasn't foreign investment, and the Chinese are astoundingly nationalistic.
Consequence of capital controls.
People didn't want to miss out. That's it.
You're not going to buy a house on 3:1 leverage if you think it's overpriced by 30% just because you think the stock market is overpriced by 50%. You'd just keep your cash in savings.
The problem is - they believed it would keep going up - because it had been for almost everyone's entire adult life.