That oversight comes as a total shock to Oscar pundits -- arguably the year's biggest snub, alongside the fact that Selma placed in only two categories (for which theories abound). From the point of view of the animation community, however, there was always a risk, and here's why.
1. Animation professionals pick the nominations
At this stage in the Oscar race, it's the die-hard animation pros who decide the noms. The Lego Movie may have been the year's top animated movie in the public's eye, earning more than $257 million and placing second highest on Rotten Tomatoes' (adjusted) best-reviewed list of 2014 with a 96 percent fresh rating, but that doesn't mean it represents the kind of artistry that the industry wants to celebrate.
[ Review/Trailer: The Lego Movie ]
2. A record number of eligible toons means tougher competition
Back in 2001, when the Academy first added the best animated feature category, it wrote in a rule that in a year when fewer than eight toons opened in theaters, the prize wouldn't be awarded at all. In retrospect, that seems laughable, considering how the medium has boomed, resulting in an all-time high of 20 Oscar-qualifying submissions fighting for five slots in 2014.
3. Voters watch all 20 contenders, so the best rises
Unlike normal audiences (or the Academy at large, who often pick a widely seen film to win), the animation branch is obliged to screen all eligible contenders. Each film is scored on a 10-point scale, and the five that receive the highest score go on to be nominated. That means each toon is considered on its own merits, and for this group, technique is perhaps the most important. In other categories, nominations go to the five films that received the most first-place votes, resulting in a diversity of choices, but in this category, it's literally the five movies the branch likes best.
[ Related: The 17 Biggest Oscar Nomination Snubs and Surprises ]
4. The animation branch loves handmade movies
This is the second time popular Lego directors Phil Lord and Chris Miller have been edged out of the Oscar race by a pair of tiny toons most moviegoers haven't heard of: The same thing happened in 2009, when Cloudy With a Chance of Meatballs got shut out in favor of The Secret of Kells. While the Lego team licks its wounds, the folks no doubt celebrating today are New York-based indie distributor GKids, which released two of the nominees: Song of the Sea (a dazzling, highly stylised 2D toon from Kells helmer Tomm Moore) and The Tale of Princess Kaguya (a career-crowning hand-drawn beauty from Japanese animation maestro Isao Takahata). Also celebrating today is Portland-based Laika Studios (Coraline, ParaNorman), which earned its third nomination for its third feature, The Boxtrolls. Industry pros love stop-motion. It's by far the most painstaking form of animation there is, whereas the computer-animated "LEGO" was cheekily designed to parody bad stop-motion.
5. Traditional forms and classical storytelling win out
Song of the Sea, Princess Kaguya and Boxtrolls were always going to be nominated. That left just two slots open for the remaining 17 movies. The very same reasons the general public loved Lego -- its jokey tone, quick pace and irreverent sensibility -- probably worked against it with that group. After all, how often does that kind of movie get rewarded in other Oscar categories? By contrast, Big Hero 6 and How to Train Your Dragon 2 are both relatively traditional, well-told stories hailing from studios (Disney and DreamWorks, respectively) with a long tradition of Oscar support. Lego fans shouldn't conclude that the Academy doesn't like that movie; it's just that they respected five films more.