The big caveat for this post is the fact that it is entirely subjective and based on my perceptions of the general media, and also the reactions of other people. Keep that in mind, but feel free to correct me if I'm an idiot about these claims or theories.
"Frozen" seems to have been a quiet arrival. Based on my research the pattern for its release is the same as "Wreck-it-Ralph." Both films were released in November, (oddly enough, both films involve a character who is wrongfully viewed as "evil") both films had a trailer released in June, and other around September. One big difference is the fact that "Frozen"'s first trailer was basically just a gag and didn't actually give any sense of what the movie was about, nor that it would actually feature human characters. This means that most people probably didn't know much, if anything, about "Frozen"until just two months before it was released.
Now, this is just a theory, but I have a notion that people's expectations about a film have a certain kind of dependence on the amount of time they have to process those expectations. If a person has more time to consider the film, they have time to talk themselves out of it. A person's anticipation for a film can greatly diminish if they have a long time to consider it, and know what is coming.
Another element that becomes part of this is the social media. I don't think there were a great many people sharing the first trailer for "Frozen." It's fun, but it's not super-interesting. Even if people did see it, it's a bit forgettable. There's not real information for the film.
The second trailer has more content, and it also started the campaign about female empowerment. (I know better than to really get into that topic here, but you can't really talk about "Frozen" without it.) That angle on the promotions probably gave an extra edge to the film's appeal.
This might not be an exhaustive analysis (I'm still new at this), but I hope it is worth thinking about. People like a new approach to things. "Frozen" provided that in the content, the angle, and the pace of the advertising, and this may become the norm if Disney can replicate it properly.
