From wikipedia

At the show, presenters Faye Dunaway and Warren Beatty read La La Land as the winner of Best Picture. However they had mistakenly been given the Best Actress envelope, for which Emma Stone had won for her role in La La Land moments prior.

I'm starting to think theses controversies are artificially induced and envelopes with recipient names are deliberately "mixed up" or ambiguous to manufacture drama in the aftermath so people can have something to talk about.

Otherwise what else could we talk about? "So, like, this movie was awarded a movie award by the movie industry award panel at the movie industry award-giving ceremony last night... cool, pass the beer nuts".