The group’s propensity for violence and extremism was no secret. But the F.B.I. and other agencies had often seen the Proud Boys as they chose to portray themselves, according to more than a half-dozen current and former federal officials: as mere street brawlers who lacked the organization or ambition of typical bureau targets like neo-Nazis, international terrorists and Mexican drug cartels.

“There was a sense that, yes, their ideology is of concern, and, yes, they are known to have committed acts of violence that would be by definition terrorism, but we don’t worry about them,” said Elizabeth Neumann, an assistant secretary for threat prevention in the Department of Homeland Security who left last year. “The Proud Boys are just the guys-that-drink-too much-after-the-football-game-and-tend-to-get-into-bar-fights type of people — people that never looked organized enough to cause serious national security threats.”…

“They committed violence in public, used videos of that violence to promote themselves for other rallies and then traveled across the country to engage in violence again,” said Mike German, a fellow at the Brennan Center for Justice at New York University and a former F.B.I. agent who worked undercover among right-wing groups. “How that didn’t attract F.B.I. attention is hard for me to understand.”