I'm on the record here as against prosecutorial discretion, but the Rittenhouse case is a prime example of why it needs to exist -- albeit regulated, at least.
Without proffering an opinion on what Rittenhouse did, there's not enough to prove reckless or intentional homicide beyond reasonable doubt, which is in the final analysis the evidentiary standard in play. Wisconsin doesn't impose a statutory duty to retreat, and despite this Rittenhouse attempted to retreat, was followed, and after which he was assaulted in a forcible attempt to disarm him. Any reasonable person in that circumstance would have cause to believe themselves at risk of death or serious bodily harm, which is the standard for use of lethal force in self defense.
The homicide charges never should have been pressed, because they're highly unlikely to yield conviction and therefore weaken prosecution's case overall. The only reason they were, was because of the politically controversial nature of the case. Prosecution should have stuck to the reckless endangerment and firearms charges.