It’s because this is what Communists do in order to take over a country. They foment violence, coalesce around a solution that gives government more power, they blame the existing leaders and say it is time for a change, they get their media and useful idiots to help maximize the awareness and finally after they take power, they kill their opponents.
We have only seen this, how many times in the last 100 years? Unfortunately there is a tipping point where this cannot be reversed and we are fast approaching it. As long as Trump stays in office, we will somehow manage. After that, all bets are off.
Not just communists, but any authoritarian ideology controlled by and for the benefit of a small elite leadership