Earlier quoted context omitted.
60% of Republicans believe that Biden did not win the election. If you believe the presidency has been stolen by a conspiracy then violence is the only recourse remaining. This is not a handful of extremists. This is the predominant view.
And about the same number of Democrats believe the widely debunked conspiracy theory that Trump colluded with the Russians to interfere with the 2016 election or that members of congress were paid Russian assets. That's the thing about polarization. It's easy to see the crazy when it's your political enemy doing it.
A number of other people went to jail among the "Russiagate" investigation. It is true that none of this has ever quite reached Trump himself.