My first thought when the wrong film was announced for Best Picture was, why didn't the presenter's catch the error? Then the correct card was shown on screen and the reason became clear, incredibly poor design. Here's a great explanation:
I would imagine there are multiple redundancies so that something like this does not happen — especially at the Oscars! But there’s one thing the Academy possibly didn’t consider, or forgot, for this year’s winner cards: typography. […]
That’s horrible typography. I will emphasize horrible again. Horrible. Or to be nicer, not good. Look at it again. Of course, anyone could’ve made the same honest error!
The words “Best Actress” is on there — at the very bottom — in small print!
You are on television with millions of people around the world watching. You are a little nervous, and you have to read a card. You will most likely read it from top to bottom (visual hierarchy) without questioning whether the card is right. That look on Warren’s face was, “This says ‘Emma Stone’ on it.” Faye must’ve skipped that part and was caught up in the excitement and just blurted out, “La La Land.”
I don’t blame Faye or Warren for this. This was the fault of two entities: whoever was in charge of the design of the winning card (Was it really a design? C’mon), and the unfortunate person who handed them the wrong envelope.