"There are some incredibly smart people involved with Antifa. Some of them issue calls to stand down when a bad scene is likely to occur, and they are taken seriously.
The fact that Antifa did not show up on 06 January was one of those: the call went out to avoid DC, and people listened."
This reminds me of media tale that I heard about a would-be 'recruit' to Antifa. He was encouraged to attend a demonstration and then the 'recruiter' bailed and never showed up 'because of the potential for violence'. The would-be recruit to steal a phrase had, "A history of violence". The wannabe was discouraged by the episode and sought treatment for his issues and now seems to be on the way to reformation.