Before she won an Oscar for designing the costumes in Mad Max: Fury Road, Jenny Beavan learned a powerful lesson on confidence from Charlize Theron, which is maybe what inspired her to arrive at the ceremony rocking pants and a leather jacket. In real life, that's a very normal outfit; at the Oscars, it's practically sacrilege — a point the bigwigs in attendance helpfully underlined by reacting like prudish Victorian schoolmarms. Look at that guy's eyebrows! I've seen subtler reactions from a cartoon wolf.
Update: Obviously a six-second clip can tell an incomplete story. Alejandro G. Iñárritu, winner of the Oscar for Best Director for The Revenant and one of the men who appears in the Vine, has issued a statement clarifying that he did clap for Beavan:
I think Jenny Beavan is a masterful costume designer and very deserving of the Oscar for Mad Max: Fury Road. By editing and omitting the full reality and suggesting I felt anything but admiration is mean-spirited and false. What you don’t see in the 10 second clip being circulated is my applause for Jenny as she ascended the stairs to the stage. I’ve learned a lot this awards season … that I should never cross my arms when I am sitting down.
There's also an alternate GIF from the telecast, which indeed shows the director heartily applauding.