If the testimony, under oath, is correct, the last thing that Joseph Rosenbaum did was shout "Mother fucker" and lunge for Kyle Rittenhouse's gun.
I want you to run this through your brain if you still can't see that Rittenhouse is innocent.
What if Rittenhouse hadn't fired and Rosenbaum had managed to disarm him, turned the gun on Rittenhouse, and killed Rittenhouse with his own gun. Rosenbaum had threatened the lives of Rittenhouse and others during the course of the night leading up to the incident.
If Rosenbaum were on trial for murder with all of the events leading up to the altercation being exactly the same with only the altercation ending differently, would you believe for a moment that Rosenbaum would be innocent?