Unfortunately we'll probably always be in the dark about the HOW, WHO and WHY. :(
If it was an honest mistake, they're not going to publically throw an employee under the bus.
If it was a malicious action from the NSA, they're not allowed to make it public.
I suspect the only hypothetical way we'd hear about the "who" is if an employee weakened it for his own personal gain, and criminal charges were raised.