What I want to know is why the FBI even cared in the slightest that Jason broke Brian's wifi for an hour. I feel like there must be something missing to this story to explain that.

Indeed – in the past, even if you suffered actual damages the first thing the FBI would ask was whether they were over $50K because they didn't touch anything under that amount. I wonder if most of the appeal was a case where all of the participants are known & local – they're thinking a quick, easy prosecution and some press to pad someone's annual review.

Sometimes they prosecute these cases just to gain experience in prosecuting them.

Good question. Who calls the FBI over something like that? Granted, I haven't heard his side of the story, but with the information I have now I don't ever want to be friends with Brian.

Based on other comments & Occam's Razor tells me that Brian banned Jason's email account then Brian started to DDoS Brian's WiFi at which point Brian contacted FBI.