To be fair, Brave did play to the Oscar crowd better than any of the other films. The mother daughter relationship, the solution for the conflict, the landscape/setting, etc… seems like something the Academy would eat up even though the effects were better in ParaNorman or the narrative/character dynamic was better in Ralph.
However, the theme both Para and Ralph had probably diminished its chance for success. Obviously both were great movies, otherwise they wouldn't have been nominated. Yet, there are a few nit picky things that probably caused them to lose to Brave. For example, how often does a Horror or Video Game motif play with the academy? Even though both movies did something remarkably clever with both themes/motifs, I don't think the Academy ever warmed up to anything involving Horror (Silence of the Lamb doesn't count) or Video Games.
For Ralph, the lingo/video game subject matter might have been too distracting for most of the Academy folks. Maybe most of them weren't gamers back in the day so the references, terminology, ideas might have not been accessible to them (in spite of the story being broad enough to be universally grasped).
For ParaNorman, the story started out very 70-80s Horror-esque which also contained a lot of allusions and concepts that might have gone over the Academy's head (hence ended up being distracting). Also it was really dark and violent which might not have sat well with some viewers.
Frankenweeiner had the same problems listed as ParaNorman and Pirates was kinda wierd on some minor levels.
I think it is pretty clear the Academy wanted something broad and accessible so Brave seems like the clear cut decision out of the rest.