In the 1920s, the world’s wealthiest people per capita were Oklahoma’s oil-rich Osage Native Americans—but cattle baron William “King” Hale (played by Robert De Niro, 80) had a plan to murder and rob them, and perhaps his dimwitted nephew (Leonardo DiCaprio, 48) was mixed up in it. It was the first big case for FBI director J. Edgar Hoover, and now it’s a 3½-hour prestige movie by Martin Scorsese, 80.