1. Evidence seems to point that the main developer is in Europe. So, an NSA NSL doesn't seem (to me) to be a likely factor.
2. Evidence points to the history of the code perhaps being legally murky. But from what I recall of the forum discussion nearly a decade ago, most of the murk wasn't due to the code origins, which appeared to be on the up and up, but due to the legal threats/actions of a company that thought it could prevent a fork from *before* buying code/hiring the developer. That's IIRC, of course, I've seen reporting all over the map on this issue. Also, supposition: there may have also been verbal promises between the dev(s) and outside entities about what might trigger more legal issues.
3. Evidence points to English being the main developer's second language, so the conspiracy theories base on awkward sentence construction are probably just that, theories.
4. Evidence (now gone, due to the tc forums being removed) also seems to point to the main developer having strong feelings about control over the main code line and trademarks for a long time. Some of this seemed rational (wanting to block a plethora of backdoored versions being deployed) but some of this seemed personal. Most devs have been there, some have matured and learned to let it go.
Conclusion: the simplest explanation, to me, is that the main dev wants to the code dead and buried so that he is entirely free of any future legal, ethical or emotional consequences of it continuing.