“Dumb Money” whisks us back to a time in American history, the year 2020, when Keith Gill, a Reddit and YouTube demi-celebrity, cranked up the poor little GameStop stock to improbable heights. He did it from his basement in Brockton, Massachusetts. Gill, played with easy, intriguing command by Paul Dano, had a far-flung array of viral fans going along for the ride to Oz. They shared his fond ...