Rittenhouse showing up was a result of unrest in a town where he had friends and family. He gave aid to rioters and protesters as well as counter protesters. He showed up to protect and help people, and if he hadn't been armed, he could have been shot and killed or beaten to death, because he told people he was there to help the police. It wasn't until he'd been shot at, attacked with a skateboard, and had a gun aimed at him by an asshole who threatened to kill him earlier that Rittenhouse used his weapon.

I think being armed was probably responsible and it's fairly clear given the evidence from the trial that it was used in a responsible way that exemplifies the use of lethal force in self defense.

The media stoked narratives that caused the riots are to blame. Sensationalism of topics like police on black violence manipulates people into believing things that aren't true, and they react in ways that might very well be reasonable if the narratives were true. I think Rittenhouse is going to sue the ever loving shit out of a lot of legacy media corporations, and maybe that will make them a little more cautious when hyping the tabloid bullshit.