FHFA and caveat emptor

It seems that the Federal Housing Finance Agency thinks that various banks sold packages of bad mortgages to Freddie Mac and Fannie Mae..

Well, duh.

What I find interesting about this is that their contention seems to be that the banks, who bought the mortgages from originators and sold them to Fannie/Freddie, knew much more about their properties than Fannie and Freddie did - given the same public information. So the banks are being blamed for Fannie/Freddie failing to do due diligence on what they were buying. Has anyone told the FHFA what Caveat Emptor means?

On $200bn of mortgages, it looks like they're seeking redress on ~20% of it - $40bn, which is a lot of money in anyone's book. Appreciating that you probably can't find this kind of money in the bank accounts of the Fannie/Freddie employees, it nevertheless seems somewhat iniquitous that the US government (for, let's face it, they're driving this) seeks to blame private industry for the failings of government employees and seeks to make a hefty chunk of cash in the process.

Perhaps the FHFA claims that the banks did better research on the mortgages than Fannie or Freddie, and should have passed on that research for free. Perhaps it claims that the banks didn't disclose what they where statutorily required to disclose, in which case the enforcer of the statutes (the FHFA, presumably) seems somewhat incompetent. Perhaps it argues that the banks should have disclosed more than what they were statutorily required to, in which case the statutes seem inadequate. Perhaps it argues that the mortgages should have been sold cheaper in hindsight, which is an interesting perspective on contract law.

Perhaps the FHFA has been a serious waste of Federal money over the past five years and is desperately seeking to camouflage this?