Because NIST chose it, after non-public input from the NSA. But if I am honest, NIST recommending it at all is enough to suspect it of being compromised. I say that as an American, and my non-american friends equally don't trust NIST on crypto topics.

The real problem I have is best described as I haven't read a single coherent argument responding to and rejecting the real concerns raised by the individual who after nist betrayed the internet with by recommending a compromised standard at the encouragement of the NSA. Is the person who wrote the crypto library everyone uses.

DJB puts his money (time) where his mouth is. I would critique his attachment to his own ego. But I'm in the group of people who haven't contributed enough yet to foss to get to throw stones. So I'll defer to people who can match his contributions. Until that happens, DJB's reputation is cares passionately about crypto and it's community, vs an US government group with a reputation for trying to sabotage crypto systems after passing secrets with the NSA, who refuses to provide details about their most recent secret messages.

I do find some of the arguments and refutations from the mailing lists compelling. But not all the them, and nothing directly from NIST. Equally some of DJB's appear to weaken his points. But like I said, I plan to trust the reputation each party has earned.

NIST has a history of behaving inappropriately, and unethically around it's cryptography recommendations. But the people currently in charge would rather pretend they're above it and not literally directly responsible for the organization with a well earned reputation. If you're given a 2nd chance after your partner catches you cheating, it's a reasonable requirement that you account for every second of your time, until you restore the reputation you destroyed.