Lest we forget, they built huge apartment blocks which were never populated.
They were all speculative real estate ventures and were never meant to be lived in - further the construction was so poor that had they been occupied, they would not even last the year of so that buildings that are lived in last. Many of the vacate building do not even have stairwells in them, nor windows or doors; they are just shells.
Much of this behavior stems from the fact that all land in China is owned by the CCP which leases the land for only 70 years before it reverts to the CCP.