It isn't about real talent and the best movie, it is motivated by political correctness. Broke Back Mountain didn't get nominated because it was a hell of a movie. It got nominated because it was the first queer movie with big names playing in the starring roles. A few more recent examples, Fahrenheit 9/11 & Inconvenient Truth.
Most Best Picture winners are fairly conservative actually. BM was one of the best reviewed films of the year and it didn’t even win. F 911 wasn’t nominated for any Oscars! Besides I’m talking about the dramatic awards which are generally pretty good.