The evidence the prosecutors will present will be his own words about going there to protect property, and the fact that he illegally obtained a firearm and crossed State lines to seek out the protestors. The ideas both that he confronted the protestors and that they rightly perceived a threat from him will easily follow from this. Rittenhouse is in a tough spot, as he literally told anyone who would listen that he was going there to protect property (obviously by playing vigilante and confronting those whom he was protecting the property "from".)
(They will try to add further support to this by introducing evidence of his past, violent behavior, during which he inserted himself in a violent a situation and increased the violence, instead of trying to stop it)
That's twice I have posted most of this this directly to you. Again, PLEASE try to do a better job of following.