I'm probably skipping some steps, but lowtax banning hentai drove the weebs to 4chan, and 8chan. 8chan was the home for all the "Q" posts that started Qanon which riled up the Republican base and led to the Jan 6 insurrection
Christopher Poole founded 4chan because some hentai-relates things were banned on something awful. 4chan's /pol/ was an early seedbed for right wing extremism. Also the first QAnon posts came from 4chan.
Bunch of degenerates are terminally online on an almost anything goes website.
Stormfront and others see the site as ripe for manipulation and recruiting.
Over a decade, 4chan is dragged rightward by concerted effort from various fascist groups.
Manipulation of social media increases into the 2010s, fueled now by governments attacking mostly the USA and Europe.
QAnon gains popularity after others on 4chan fail; CIAnon, FBIAnon, etc etc. Right wing, hateful, insane, or just plain dumb normies all slurp up the conspira-juice.
russian asset becomes president. Incompetently tries to destroy government and nation while stealing as much as possible.
russian asset loses election. Decides to try to destroy the USA a bit more by declaring the election fraudulent without a shred of evidence. Tries hard to get result flipped to republicans for... reasons.
Dumb ex president thinks he can just demand Congress elect him. Holds a rally the same day as the election is certified, tells attendees to "fight for America's future, let's march to the Capitol, I'll be right behind you!"
After they organized partially on 4chan, Enthusiastic chodelet troglodytes storm the Capitol.
There's a great documentary call Q: Into the Storm that was on HBO that covers the history of how Qanon came to be. The short version is what the other person who replied wrote.
The first part there is a big reason behind why 4chan was started and the big block relates because a lot of the far rights coordination online stems from 4chan and 4chan initiated movements. I'd argue pepe and all the memes around Trump was instrumental in getting him elected 2016 and that started on 4chan. Also the whole qanon thing had a lot to do with 4chan and that was a big part of why Jan 6th went down.
"...had a lot to do with 4chan" here means 4chan deliberately initiated the entire movement with the express purpose of causing harm for their own amusement