It's strange that owners would let the homes go vacant rather than rent them via a property manager. While the article seemed well-researched, one missing bit was who purchased the mansions they kept mentioning. They knew the builder, so perhaps they could have asked.

Is it though? Some of them just want to move their money outside of China incase something happens and they don't really care about anything else. While renting them via a property manager is a better financial decision, i'm don't know if you they care about it that much they are paying $x above asking price. Also, this might be their vacation home.

Yes, making a poor financial decision is strange when it's so easy (on the face of it) to make a better choice.