I just read the full original paper, and this seems like the most likely explanation to me:
"[T]he main considerations might not have been technical at all, but rather Agency-specific — that is, related to the difficult situation the NSA was in following the Snowden leaks. The loss of trust and credibility from the scandal about Dual EC DRBG was so great that NSA might have anticipated that anything further it said about ECC standards would be mistrusted. The NSA might have felt that the quickest way to recover from the blow to its reputation would be to get a “clean slate” by abandoning its former role as promoters of ECC and moving ahead with the transition to post-quantum cryptography much earlier than it otherwise would have."
I spent >10 years working for the government, and this scenario is entirely consistent with my experience there.
"[T]he main considerations might not have been technical at all, but rather Agency-specific — that is, related to the difficult situation the NSA was in following the Snowden leaks. The loss of trust and credibility from the scandal about Dual EC DRBG was so great that NSA might have anticipated that anything further it said about ECC standards would be mistrusted. The NSA might have felt that the quickest way to recover from the blow to its reputation would be to get a “clean slate” by abandoning its former role as promoters of ECC and moving ahead with the transition to post-quantum cryptography much earlier than it otherwise would have."
I spent >10 years working for the government, and this scenario is entirely consistent with my experience there.