Dealing with renters in that equation dosent make any sense, because the returns will be tiny, even with sky high rents like $3000 a month on say an $800k property appreciating 20% every year (a real situation in many cities). The presence of renters will ensure you cant sell it when you want to, and instead have to deal with them, an insane hassle for a foreign investor.
Compounding this is the fact that much of this property investment is being driven by wealthy (and to a huge degree corrupt) chinese looking to funnel money out of china, before the CCP can take it from them. Real estate is one of the few foreign investments allowed by the CCP. Tie this in further to the investor class visas many countries have, where you get the equivilent of a green card if you invest X millions of dollars. In these circumstances people dont care much about returns, or even taking somewhat of a haircut on their investments, because its better to have some + a get out of jail free card as a resident of another nation, than be stuck in china in jail, with no assets at all.
Your continued incredulity that these properties arnt being rented out dosent change the reality of the situation, a massive percentage of them are not, and are built specificly to NEVER be rented.