Some things went seriously wrong when investors started buying up single family homes as a source of significant returns. Historically, the cost of insurance, utilities, maintenance, and property taxes ate up so much of the return. Illiquidity and high transactional costs also meant single family homes weren't regarded as a good investment.
I suspect there was so much liquidity in the system that it just flowed into residential real estate despite the obvious shortcomings.
All these people who have turned into house flippers kind of reminds me of the people who formed investment clubs prior to the dot.com bubble bursting.