I'm not sure that this indicates a bet against the American Dream.
They are at this point holding onto the houses and renting them out.  How many that were bought at the bottom of the market have they already sold?  Are they liquidating inventory still?  Are they waiting for the markets where they own the houses to reach a peak before liquidating their inventory?  Have they pulled enough out so that all of their original investment capital has been paid off and now they are reaping the gains?  
One thing that would get them to dump their inventory would be to for "tax reform" to eliminate the deduction for interest expense.