You're argument is that I shouldn't think of NIST as a patsy for the NSA, is because the NSA can't possibly be recommending a compromised cipher, because if they were, that would mean this US government org is horribly defective and dysfunctional, where one side didn't know what the other was doing?
Incentives are basically all I consider when trying to establish true motive. But you're not required to consider motive when there's a history or pattern. Even if "It's the way we've always done it", wasn't a much, much stronger motive than thought/reason is for any human. It's both logical and desired to treat something as the most dangerous until proven otherwise.
I used to be a nurse. I remember when working in the ED, I was taught that every single woman on childbearing age who comes into the ED with abdominal pain is an extopic pregnancy until proven otherwise. If you ask a woman if it's possible she could be pregnant, regardless of the truth, many will claim it's impossible. If you blindly trust them, and delay treatment, you could needlessly kill your patient, or leave them infertile. Why would someone lie and risk that? Or how dare your medical team make assumptions like that? Well the alternative is worse, the reality should be easy to prove.
NIST has a history of recommending broken ciphers. That's not a mistake a professional would ever make. So thinking about incentives, I'm going to treat it like it was intentional. Here the group with a history for fucking up, isn't being transparent. I would love it if NIST would say enough to make DJB happy or at least stop pretending like they deserve any trust anymore.
Until then, I don't find "they're probably behaving like rational actors" compelling enough to trust them with keeping secrets from somebody who I actually do trust.