Didn't anyone actually watch the trial overview? Here's what came out in court.
Rittenhouse was one of around 100 people that were asked to protect businesses after days of looting and burning, because the police failed to protect the streets. While Rittenhouse is not from Kenosha, his father does live in the city and evidently many of Rittenhouse's friends also live there. Rumour has it that the police were told to stand down by the Mayor, who was up for re-election. Rittenhouse was given the rifle while in Kenosha. In Wisconsin it is legal for a 17 year old to carry a long gun. Outside of cities rifles are standard in most rural areas in North America - where hunting as family groups is popular and guns are sometimes necessary to kill rabid coyotes for example.
Rittenhouse was somehow separated from his friends, and a convicted 5 times paedophile named Joseph Rosenbaum, a biopolar sufferer who had been released from a psychiatric institution the week earlier but wasn't taking his meds, attacked Rittenhouse shouting that he would kill him. Not that it's relevant but Rosenbaum forced one child to perform oral acts. After Rosenbaum attempted to grab Rittenhouse's gun the 17 year old fired three shots from his rifle killing Rosenbaum.
At this Rittenhouse was chased down the street by a mob of other people. One of these people caught Rittenhouse and started beating him, at which point he fired two more shots but hit no one. A moment later Rittenhouse is attacked by Anthony Huber and beaten over the head with a skateboard. In response Rittenhouse fired a single shot killing Anthony Huber. Huber also had a record of violence (he attacked his own grandmother).
Finally a fourth person, Gaige Grosskreutz, attacks Rittenhouse and lunges toward him pointing a pistol at him that Grosskreutz had concealed. Rittenhouse shot and wounded Grosskreutz, who also has a criminal record. Rittenhouse was not firing shots indiscriminately according to the evidence from witnesses.
As soon as he'd managed to clear the mob, Rittenhouse ran towards the police and handed himself in.
You can argue that Rittenhouse was an idiot for being present on the streets with a rifle. But there were many people on the streets with guns during that period. (In fact concealed carry laws apply in a number of states so you never know who has a gun). What is undeniable from the evidence is that Rittenhouse was attacked without provocation. There is little doubt he would have died or have been severely injured had he not opened fire, and a jury of 12 of his peers - not necessarily predisposed towards Rittenhouse - saw the evidence and acquitted.
You would know almost nothing of the above if you had only watched CNN, MSNBC, ABC, CBS or NBC. MSNBC had Rittenhouse as a White Supremacist (there's zero evidence for this) who killed dozens of black Americans (none of the victims was black).