People do on occasion, like there were armed leftists that prevented police from raiding encampments in Texas, and at some protests there have been organized armed groups like John Brown Gun Clubs or Socialist Rifle Associations. Several people that argued for more militant resistance to state violence were murdered in 2020, and many times for decades before that, so a lot of people are scared and not organized sufficiently, but there are groups that have been preparing.
People often talk about going back in time to kill baby Hitler. By all measures Trump would like to be a new Hitler and his most fervent supporters see him as that. Is it surprising people would support such an action to stop him?