The American Left does this because they want extreme amounts of rape, robbery, and murder in society. They want chaos, and a few dead citizens are nothing to the enforce "the agenda". It is just an expense for ushering in their version of utopia.
They want to disrupt American society in any way they can. As many others have said before me, the goal is to promote so much social disruption and chaos that they can declare a "national emergency" which will allow them to do away with all Civil Laws. Essentially, a national emergency and martial law would give them a free hand to implement by force what they cannot do by politics.
All of this may seem absurd and 'crazy', but it is not. Everything the Left/Democrats do is all toward a single goal. That goal is authoritarian rule over every aspect of society, and despotic rule over every aspect of your life.