Fannie and Freddie... [are] in the same business as the Fed these days.... [W]hat the Fed is doing when it engages in “quantitative easing” [is] expanding its balance sheet by buying unconventional assets... a broader provision of credit to the private sector by governmental or quasi-governmental agencies.
Why do this?
Part of what depressed the economy during the financial crisis was a widening spread between government debt and private borrowing costs--not just in things like the TED spread, but also in mortgage rates. This spread was narrowed thanks to a combination of Fed actions and the expansion of Fannie-Freddie lending. And the administration very much wants to keep this kind of intervention going.
You can argue that some other policy — inflation targeting by the Fed, expanded fiscal stimulus, whatever — would be better. But none of these things seem politically possible.
Keeping Fannie and Freddie fully engaged in the mortgage-support business is one of the few tools available to prop up a still very weak economy. And so they’re doing it.