As the Sundance Film Festival winds down its final edition in Park City, Utah, this week, ahead of its move to Boulder, Colo., next year, its sway over the nonfiction field at the Oscars remains as steady as ever. All five current Academy Award nominees for documentary feature premiered at last year’s festival, with Sundance films winning the category six times over the last decade. “It wasn’t the easiest film to get off the ground.” A similar challenge could apply to other nominees, including “Mr. “My first two films didn’t get into Sundance, and then my third one did. I’m always telling young filmmakers to use the Sundance rejection as fuel.”A festival berth was strong motivation for “Mr.