Box office doesn't matter when it comes to the Oscars.
Yes it does.
I didn't say it was the only thing that mattered. There are three paths to Oscar nominations:
1. Be a big financial success (preferably in a genre Oscar likes, but if you're sufficiently big, even if you aren't, i.e., Avatar
2. Be a big critical success.
3. Be both of those things at once (ideal!).
Or, just have Harvey Weinstein running your campaign.
But Cloud Atlas
was none of those things. Oscar voters go for their favourite movies, for the most part.