It's been explained. Warren Beatty and Faye Dunaway were handed the wrong envelope, given the one for Best Actress not Best Picture. That's why Beatty stared at it for a few seconds wondering what the hell he was reading.
Reportedly, it happened to Sammy Davis, Jr, in the '60's---he was given
the wrong envelope when announcing the winner for best music. Luckily,
he announced a movie that hadn't been nominated in that category and
they quickly corrected the mistake.
Well, I am glad La La Land didn't win and I'm disappointed that it won in other categories. It was from the director of that terrible drum-playing movie, Whiplash. Is playing the drums so alien that people believe nonsense like that? I know professional jazz drummers and they thought it was absurd.
Why do they broadcast the Oscars live in the first place? They're celebrating movies. Movies are fake. They shoot retakes. Think of how pleasant and stress-free it would be for everyone involved if they shot the whole thing on videotape a few days before, perhaps in front of a green screen with a laugh track.