We can play the blame game all the way back to Chauvin, gutting of mental health facilities, slavery, etc but Kyle decided to insert a rifle into a situation that neither he, nor the rifle, was invited to. He went looking for problems to solve, strayed far from the group he was seen with/the police/safety/etc and naively went towards the rioters and protesters.
Regardless of morality or the law, that decision has ruined his life and caused the death and injury of multiple others. They were turbo dumb for chasing him, but Kyle was astoundingly stupid to drive from his home and come to Kenosha. He was looking for trouble to solve, got in too deep and like the untrained and dangerous fool he was, shot his way out of it.