People aren't talking about it but hedge funds and pension funds are also buying these houses because rental properties are safe, long-term investments. Try outbidding a hedge fund. You'll fail every time. They've protected these investments by massively outbidding other potential buyers on tens of thousands of homes. This raises the average home prices and sets a precedent for other comp homes in a given area. They keep their investment "valuable" because it is now scarce. They've effectively raised the barrier of entry for new home buyers to a level that is almost unobtainable for the foreseeable future.
I foresee these homes coming back onto the market in 10-15 years completely trashed when these people have gotten the mortgages paid off and want to dump them. They likely will have done the absolute minimum to maintain these properties. The 2% interest loans will allow these people to make plenty of $.