All of this is very possible, but let's not get ahead of ourselves like we have the proof already.
When people accept something as a fact without proof, even if they are right, they stop looking for proof as hard as they otherwise would.

Also there wasn't one "kid", there was a whole team of researchers.
And the "BITCOIN is NSA" part, a bit of an overreach, not that it would mean that Bitcoin is bad even if it was true.
Let's not forget that Tor was developed by US military and also the Internet and neither was a secret nor was bad for humanity.

Sometimes government agencies want to be anonymous as well. Especially if they like getting involved in other government's business.

It is not that black and white. Sometimes governments need to mask their operations by hiding in the crowd, so they gift the weapon to all, so no one knows when they use it and when their weaker enemies use it.
And when their weak enemies use it, it just gives them more justification for their existence.