This could only be based on the idea that the cost of foregone debt servicing (i.e., monthly mortgage principal an interest payments) is less than the ultimate cost of having a foreclosure, an empty property sitting in REO inventory with vandalism and rehab costs (e.g., mold infestation) that they think can be avoided by having a non-paying mortgagor in the house.
Maybe that is correct, maybe not. But all that Freddie Mac and Fannie Mae are up to now is loss mitigation. And since the losses net out to the injury of the taxpayer, we had better hope this is indeed correct.
It just delays the inevitable and allows for them to not really give a crap about the condition of the property. These are not your ordinary unemployed, these are people that moved into a place they knew they weren't going to be able to afford too long.