To understand the rationale behind this change requires a dark journey into the minds of head Disney marketeer MT Carney and studio chief Rich Ross. The duo, under still relatively new CEO Bob Iger, inherited an unprecedented problem for the company.
For the lion's share of the Walt Disney Company's existence, it's most successful films operated by a simple formula: they each had a proper name. Snow White and the Seven Dwarfs, Bambi, Pinocchio, Peter Pan, Cinderella, Mary Poppins, Davy Crockett. Certainly there were outliers - 20,000 Leagues Under the Sea is more of a vague description - but consider the case of 1940. If people think that one Disney film a year is spreading the creativity thin, 1940 saw the release of two! They were Fantasia and Dumbo. Guess which was the more popular. If you said "Dumbo" you were correct. Fantasia is merely a noun, which was insufficient.
After the death of the Mousetro, a strange change crept upon the company's films. Proper names started to lose their lustre, and chains of descriptive nouns took over. The Little Mermaid, Beauty and the Beast, The Lion King. To hedge their bets, they did preface each film with the possessive name "Walt Disney's" or just "Disney's", but the success of these films was unprecedented. It was the second renaissance.
Again there was the odd outlier, like Aladdin, but the animation department got too full of itself and started to think that the renewed popularity of their films had to do with their quality and not their titles. This led to a series of properly named box-office bombs: Pocahontas, Hercules, Mulan, Tarzan, Treasure Planet.
A proper name and a subtitle?!
Former Disney CEO Michael Eisner suspected that it was traditional animation itself that was to blame, especially with the variously-titled successes of sister studio Pixar. However, Disney's CGI films fared no better. Alas for Chicken Little. So when it came time to recapture the magic of traditionally-animated fairy tales, the choice in title was obvious: The Frog Princess. Or better yet, throw in a conjunction and an extra definite article, just to be sure. The Princess and the Frog, heir to Beauty and the Beast.
But it failed. Inexplicably, The Princess and the Frog did not live up to expectations. To make matters worse, Rapunzel was coming down the pipe and the future of the animation studio depended on it. They looked once more to Pixar, to indeterminate results. WALL-E and Ratatouille had proper names but were still fairly modest. Cars had a noun but did well in merchandise. However Up was quite successful.
Therein lied the answer: adjectives. Unmodified adjectives. Pixar's upcoming The Bear and the Bow became Brave and Rapunzel became Tangled. I am frankly surprised that Disney is entrusting Winnie the Pooh to a proper name instead of calling it Stuffed. To be extra careful, they even removed the possessive from "Disney", effectively turning it into an adjective as well. And lo, Disney Tangled did fairly well, even outpacing Disney Tron: Legacy (a proper name and a subtitle) and the complicated grammatical mess that was Prince of Persia: The Sands of Time. Sorry Pirates of the Caribbean: The Curse of the Black Pearl, lightening only strikes once.
Given all of this, you can appreciate the bind that Carney, Ross and Iger find themselves in with John Carter of Mars. That's two proper names and a preposition. That's almost a subtitle away from being Prince of Persia all over again! At least now they're dropped the preposition and the second proper name. All they need to do is figure out an adjective to replace John Carter and they're ready for a confident release.
Now if only this explanation were any more absurd than the actual reason: Mars Needs Moms blew it at the box office.