The signs were there for President Donald Trump since 2016. Therefore he had at least four years to develop a detailed and effective strategy to deal with Antifa, BLM,etc, and all domestic and foreign terrorists and anarchists, as well as plan for proper policing of riots, vandalism, looting, anarchy etc. which would involve any and all law enforcement agencies at his disposal for rapid response deployment. Please note (from the article below) that "In June 2017, the antifa movement was linked to "anarchist extremism" by the New Jersey Office of Homeland Security and Preparedness", but Mr. Trump did not take this report as a WARNING SIGNAL and move effectively against this Movement.
Here is a summary from Wikipedia [only for convenience], which is clearly Left leaning, and may be trying to minimize the violence of Antifa, while falsely calling Yiannopoulos a "provocateur", Patriots Prayer "far right", and Unite the Right as "white supremacists", which is all derogatory, while falsely calling Antifa "peaceful activists":
'Antifa groups, along with black bloc activists, were among those who protested the 2016 election of Donald Trump.
They also participated in the February 2017 Berkeley protests against alt-right provocateur speaker Milo Yiannopoulos, where they gained mainstream attention,with media reporting them "throwing Molotov cocktails and smashing windows" and causing $100,000 worth of damage. [Note: "alt-right" is the derogatory Leftist term for conservatives]
In April 2017, the Direct Action Alliance and the Oregon Students Empowered, described as "two self-described antifascist groups", threatened to disrupt the 82nd Avenue of Roses Parade in Portland, Oregon after hearing that the Multnomah County Republican Party would participate. The parade organizers also received an anonymous email, reading: "You have seen how much power we have downtown and that the police cannot stop us from shutting down roads so please consider your decision wisely". The two groups denied having anything to do with the email. The parade was ultimately canceled by the organizers due to safety concerns.
On June 15, 2017, some antifa groups joined protesters at Evergreen State College to oppose the far-right group Patriot Prayer's event. Patriot Prayer was supporting biology professor Bret Weinstein who became the central figure in a controversy after he criticized changes to one of the college's events. In addition to peaceful antifa activists who held up a "community love" sign, USA Today reported that one slashed the tires of far-right activist Joey Gibson and another was wrestled to the ground by Patriot Prayer activists after being seen with a knife.
In August 2017, antifa counter-protesters at the Unite the Right rally in Charlottesville, Virginia, reported The New York Times, "used clubs and dyed liquids against the white supremacists".Journalist Adele Stan interviewed an antifa protester at the rally who said the sticks carried by the protesters were a justifiable countermeasure to the fact that "the right has a goon squad". Some antifa participants at the Charlottesville rally chanted that counter-protesters should "punch a Nazi in the mouth".Antifa participants also protected Cornel West and various clergy from attack by white supremacists, with West stating he felt that antifa had "saved his life". Antifa activists also defended the First United Methodist Church, where the Charlottesville Clergy Collective provided refreshments, music and training to the counter-protesters. According to a local rabbi, they "chased [the white supremacists] off with sticks".
Groups that had been preparing to protest the Boston Free Speech Rally saw their plans become viral following the violence in Charlottesville. The event drew a largely peaceful crowd of 40,000 counter-protesters. In The Atlantic, McKay Coppins stated that the 33 people arrested for violent incidents were "mostly egged on by the minority of 'Antifa' agitators in the crowd". President Trump described the protesters outside his August 2017 rally in Phoenix, Arizona as "antifa".
Portland's police chief said that antifascist and anarchist protesters at a June 2017 event in downtown parks in Portland, Oregon launched objects at police using slingshots. Protesters and the American Civil Liberties Union criticized the Portland Police Department's use of crowd-control weapons, saying it was disproportionate to "the behavior of a handful of antifa protesters" in the crowd.[ACLU has always sided with thugs and criminals against law enforcement]
During a Berkeley protest on August 27, 2017, an estimated one hundred antifa protesters joined a crowd of 2,000–4,000 other protesters to confront alt-right demonstrators and Trump supporters who showed up for a "Say No to Marxism" rally that had been cancelled by organizers due to security concerns. Protestors threatened to smash the cameras of anyone who filmed them. [Note: here is proof that Antifa is Marxist, since they opposed "Say No to Marxism"]
Jesse Arreguin, the mayor of Berkeley, suggested classifying the city's antifa as a gang. [Note: this is exactly when Trump should have declared them as "Domestic Terrorists" and installed effective countermeasures to arrest them and prosecute them]
The far-right group Patriot Prayer cancelled an event in San Francisco the same day following counter protests. Joey Gibson, the founder of Patriot Prayer, blamed antifa, along with By Any Means Necessary, for breaking up the event.
On January 20, 2018, antifa protested "A Night for Freedom" hosted by far-right social media personality Mike Cernovich at the nightclub FREQ in Hell's Kitchen, Manhattan. Protesters attacked partygoers spilling out of the venue, including a 56-year-old man taken to Bellevue Hospital in stable condition after allegedly being choked and punched. David Campbell, aged 32, subsequently pleaded guilty to two counts of felony assault for his role in the violence and was sentenced to 18 months in jail.
In June 2018, a Nebraska antifa group published a list of names and photographs of 1,595 Immigration and Customs Enforcement (ICE) officials, drawn from LinkedIn profiles. [Note: Antifa and the Radical Leftists had started targeting law enforcement officers at this point, if not earlier]
In November 2018, police investigated the antifa group Smash Racism D.C. following a protest outside the home of The Daily Caller founder Tucker Carlson, who has been described by the Associated Press as "a major supporter of President Donald Trump and his policies". Activists of the group said through a bullhorn that Carlson was promoting hate and chanted "We will fight, we know where you sleep at night!" and defaced the driveway of Carlson's property by spray-painting an anarchist symbol on it. Twitter suspended the group's account for violation of Twitter rules by posting Carlson's home address. The group also posted addresses of Carlson's brother and a friend who co-founded The Daily Caller. [Note: anyone who is familiar with Tucker Carlson knows that he is definitely NOT a hate monger, but he is also very outspoken about the evil deeds of the Leftists]
In February 2019, anti-fascist activists marched in celebration through Stone Mountain, Georgia as a white supremacist, neo-Confederate rally planned to be held at the adjacent Stone Mountain Park was cancelled due to infighting and fear of personal safety...' [Note: since white supremacists are not the ones involved with anarchy in America, this would be an attempt by Antifa to make itself look good]
There may be many other reports which were not included above. Antifa ravaged Portland, Oregon for a long time.