This was their plan all along - to incite violence and rile up their hoards of Antifa & BLM to run wild in the streets.
They never thought Joe would win, even with the rigging. That's why it was all done so sloppy. The point was to produce enough votes so they could temporarily create the narrative he won. But they knew all along that it wouldn't last. They figured their media magic could convince people that Trump is a dictator and won't leave office, so he must be removed by force. That is what they're trying to gin up now. It's was and is their only option.