I don't understand this. What does the NSA get out of it? Developing it to study cryptography? Why not, but then why release it publicly? The fact that Bitcoin didn't replace fiat currency is something we know now, but recall that it was considered a possibility at the time. In the end, it just cost a lot of people a lot of money. Say what you want about the NSA, I don't think they would create something with a huge downside and no upside for them into the public for shits and giggles.
A transparent ledger which is easy to audit, for the purpose of catching cybercriminals.