Maybe they are a friend? Maybe I offered a beer to them in the next round? Maybe I offered to hook him up with a chick to suck his cock. Who cares! The premise of why they agreed to watch my shit doesn't matter for something like this.
No, the point is Kyle and his people were legally allowed to be where they were on private property. Riots showed up and attacked Kyle. He had to defend himself. That is all the salient points in this case. The only wonky thing is the age bit in Wisconsin, and the fact that maybe on of the shots went astray to hit someone not "part" of the people attacking him. However, the legal system in the past has treated all people of the same crowd as sharing much of the same responsibility.
That is factually incorrect per your own link. Rittenhouse left that property & was denied returning by the cops. The shootings took place elsewhere.