It is very possible that there were some leftist agent provocateurs, just as there were right wing agent provocateurs at BLM protests/riots.
DEBUNKED
http://https://www.snopes.com/fact-c...p-mob-capitol/
"Some right wing figures pointed to John Sullivan, an accused agent provocateur who filmed the death of Ashli Babbitt, an Air Force veteran and Trump supporter who was shot by police when she tried to break through a barricaded door as rioters broke into the building. Sullivan was arrested in Utah on Jan. 14, 2021, on charges related to the riot.
For example, right wing junk site Gateway Pundit’s headline reported, “BREAKING: FBI Arrests Antifa Leader John Sullivan in Utah After Storming US Capitol …Update: With FBI Affidavit.” The story was tweeted by “Happy Days” actor and Trump supporter Scott Baio. The unfounded claim has even been embraced by some members of Congress, including U.S. Rep. Mo Brooks, R-Alabama, who has come under fire for an incendiary speech at a rally that preceded the mob attack on the Capitol.
But Sullivan, a Utah resident, isn’t an “antifa leader,” and the idea that he’s part of the Black Lives Matter movement was rejected by the local chapter in his home state, as The Intercept’s Robert Mackey noted in a detailed analysis:
“In fact, Sullivan is a curious figure who is treated with suspicion or outright hostility by a number of left-wing organizers associated with Black Lives Matter and antifascism in Utah, California and the Pacific Northwest.”
Mackey went on to report that left wing activists in various cities have warned against associating with Sullivan, accusing him of harmful actions and exploiting protests movements for personal gain.
The FBI said during a Jan. 8, 2021, news conference that there was “no indication” that anyone from the antifa movement was involved in the attack. House Minority Leader Kevin McCarthy, a California Republican who has been an outspoken Trump supporter, bluntly rejected the claim that the riot was instigated by left wing activists, stating, “Some say the riots were caused by antifa. There is absolutely no evidence of that. And conservatives should be the first to say so.”https://theintercept.com/2021/01/14/...ashli-babbitt/
"Despite the skepticism about him on the left, the far-right hysteria over Sullivan reached such a fever pitch that when I called him to talk about it on Friday night, our interview was interrupted by a woman who came up to him on the street in Washington and asked him, again and again, “Are you BLM? Are you Black Lives Matter? John, will you just answer, are you with Black Lives Matter?”
As he walked away from the woman, I asked how he answers that question. Sullivan confirmed Lex Scott’s statement that he is not a member or a supporter of Black Lives Matter and told me he had formed his own group, Insurgence USA, to work for similar goals, like an end to police brutality and racial discrimination. Asked about his politics, he said, “It’s neither right nor left; it’s completely neutral, in the middle. I’ve never voted in my life nor will I probably ever.”
That echoed comments Sullivan made in October, two weeks before the election, when he told a handful of viewers following his hourlong YouTube monologue on the possibility of an imminent civil war that he was not interested in “picking sides on right or left,” and even believed that “voting for Trump does not make you racist.”
David, The Intercept is a highly left-biased site, as is Snopes.
Snopes often gets undeserved credit for neutrality and accuracy because they do a great job debunking apolitical internet hoaxes. However, they have an extreme left bias when it comes to political fact checking. They have repeatedly refused requests for transparency in their fact-checking process, and have failed to point to a single Republican fact-checker on staff.
Honestly you can't trust either of these sites to fact check, just as you can't trust right wing sites to do it, either.
With that said, a lot of this looks like semantics. Whether Sullivan is officially affiliated with BLM is inconsequential. For example, if you go down to a BLM protest in support of what they're protesting, and then burn down a building, you're a BLM rioter. It doesn't matter if BLM doesn't officially have you on the roster.
I'm willing to have an open mind about Sullivan. Perhaps he's apolitical and simply exploiting the causes of BLM and Antifa for attention, while not having any real support for their ideology. However, he's definitely not a Trumper, and definitely was there to cause trouble. Additionally, there were other left-wing figures identified there, not just John.
However, I am also not going to say this was an Antifa frame job. I don't believe it was. I think most of the people rioting that day were on the right, but it seems likely at this point that some Antifa types were also there to egg things on further.