when he was walking around the crowd offering water and medical assistance, for hours.

And he needed a rifle for that, did he? His stated purpose for being there was vigilantism. He literally said as such during the trial. He stated he was there to "protect property" and he brought a rifle to do so. Unless that was a water pistol, he was there intending to use lethal force.

Nobody gave a shit. You can't look at all that video and act like he was this intimidating scary presence because he was armed, when it's obvious ZERO people freaked out over it that day.

Yeah, except for the people that evidently did. And obviously you don't need to immediately freak out if you see something not considered "mundane".

digusting that you're trying to turn Rosenbaum of all people, into this heroic figure

I'm literally not. Don't put words into other people's mouths. As stated by Rittenhouse himself, he came to Kenosha, armed, in order to at the very least intimidate the protestors/rioters (whatever tickles your fancy) there. Rosenbaum, who is not exactly a stable person, was not intimidated by these attempts. In a previous encounter, Rosenbaum threatened someone Rittenhouse was with at the time.

Instead of deescalating and leaving the scene, which Rittenhouse could have easily done, he decides to risk a confrontation and sticks around. When he runs into Rosenbaum again, something triggers Rosenbaum to chase him.

Oh, he decided that, did he? You know that forensics confirmed Rosenbaum had his hand on the barrel when these shots were fired, don't you? As if Rittenhouse shot once, hit Rosenbaum in the groin, and Rosenbaum INSTANTLY stopped attacking him and backed off

Well the tooth fairy didn't decide for him. I don't need forensics to see on the video used in the trial that after being shot once, Rosenbaum falls over and graps the barrel briefly, after which Rittenhouse shoots and kills him. Oh, and this is after Rittenhouse decided to stop running, turn around and shoot him.

I like how you left out that the first of the two only got shot AFTER nailing Rittenhouse in the head with a full swing of his skateboard, and that the third only got shot after HE tried to shoot Rittenhouse

Some would call them heroic after they saw Rittenhouse kill someone and tried to neutralize the shooter.

The point is that Rittenhouse was uniquely able to prevent 2 deaths by simply not going on his vigilante-stint. He could have gone unarmed if he was only going to provide water and medical assistance, but that wasn't why he went there. While the legality of his actions can be disputed, the morality of his actions is clear: what he did was deeply wrong, and he's responsible for two people dead.