NEW YORK — @Jomboy_, the curious force known in real life as Jimmy O’Brien, sat behind the giant screen connected to his computer, settling into the chair in which he’d spend 15 hours a day during the baseball season. First came tracking down the raw video of what had been an otherwise inconsequential regular-season game between the White Sox and Astros game from 2017 — though, with the help of his many devoted fans, it didn’t take long. Then came the editing, a self-taught skill that he refined during a year in film school. Finally, there was the concluding flourish, an expletive-laced, free-flowing, unapologetically on-brand chef’s kiss of an improvised voiceover that tied the whole thing together.



The masterwork, tweeted with the caption, “Astros using cameras to steal signs, a breakdown,” took less than half an hour to produce. But it arrived within a few hours of a bombshell report from The Athletic that detailed...