For no reason I’m going to point out that for every category except best picture, only the people who do that thing are supposed to be allowed to vote. Meaning, only art directors can vote for art direction, only sound editors can vote for sound editing. This usually ends up meaning that the sci-fi and fantasy movies, which actually have good art & sound, will win, because the people voting know the criteria.
But for best picture, it’s a huge number of people that get to vote, and they usually end up voting for whatever movie they like.
So when a movie like Hurt Locker wins best sound mix/editing, editing, directing, and picture, it’s easy to assume that people simply voted a “straight ticket”, or they just picked Hurt Locker for every category on their ballot because they liked it, even if they have no idea what a sound mixer is. Instead, when a movie wins all those awards, it’s because several disparate groups of voters each independently thought each thought the area of their expertise was best in that movie.