Why Kells didn't win the Oscar.
I think the 2 main reasons why Kells didn't win the Oscar (which it absolutely should have).
Up + Oscar = maximum cash for the industry.
Labeling Up with an Oscar would bring in a lot more cash than labeling a movie like Kells with an Oscar.
The idea is Up will sell well no matter what. But put an Oscar on it and it will sell exponentially better. If Kells got the Oscar it would only help it sell a little bit better.
Kells takes a hit due to the religious undertone. Even though it was not preachy and the religious aspect was very subtle. When there is any religious tone at all it will be viewed negatively by a certain percentage of the population. A movie that is totally neutral like Up is less likely to be rejected by either religious or non-religious people. A movie like Up is designed for maximum win for the most people, primarily with the motivation of profit. But at the expense of artistic quality, depth, character, etc.
It is like the difference between an heirloom tomato and a highly hybridized, genetically modified tomato. The heirloom has the most flavor and nutrition, but does not do as well for the super-mass market like a hybrid.