Anne Hathaway's dress was a safer choice, it reminded me of the Audrey Hepburn dress revival from the mid-late 1990's. I think I still have a bridesmaid's dress in Aubergine in my closet that is pretty similar. Loved her jewelry. Given her short hair, why not go Audrey Hepburn on the night when you're a shoe-in to win? In the stage musical, the role of Fantine doesn't grab your heart as much as Eponine. But in the movie version it is the reverse. All credit to Anne's performance for making us love her in that role. She should have won for the difficult Rachel Getting Married role. I loved to hate her in that role. She won for both the Les Miz performance, and also her body of work.
Anne Hathaway is a fine actress, but it's not just her skill that's causing that effect. Part of the reason for the reverse is because the relative size of the parts was reversed as well. Fantine doesn't really have a chance to grab your heart in the stage musical; she comes on, she sings "I Dreamed a Dream," and she dies. The part's almost a cameo. But when a big, A-list star was cast as Fantine and a no-name West End actress was cast as Eponine, it's not surprising that the part of Fantine is beefed up and the part of Eponine is cut down.
Anne Hathaway also won because she went on a major campaign for the Academy Award. Out of the actresses up for the award, she campaigned the longest and hardest for it. Based just on the amount of time she's spent on the talk show circuit, I'm not surprised she won.
The Eponine role was cut down a lot
in the film when Samantha Barks was cast. Dramatically it makes sense. Eponine isn't a large role in the Hugo novel. But I suspect a lot of it is because Barks is the relative no-name in the cast. The producers had been gunning for Taylor Swift or Scarlett Johansson and I would guess that if either had been cast, the part would have been at least the size it is in the stage musical.
That being said, i almost cried in gratitude when Samantha Barks came out to sing Eponine's lines in "One Day More." The quality of the vocals were no contest compared to anybody else on the stage. (I like Aaron Tveit, but Enroljas really isn't in the sweet spot of his voice.).