Fantasia was supposed to be more than just a movie that people went and saw. It was an “event” that was supposed to be attended in formal attire and assigned seating. Disney wanted to film specific segments in 3D and spray perfume into the audiences at certain times during the film. Neither of these things ever happened, but it shows the direction the creators were trying to go with the movie. The music and animation in Fantasia marked milestones in both crafts and are still highly praised.
The creation and presentation of the movie seems to be all about trying new things. The creators combined live theatre with movies and in that way made it so famous. It was supposed to be something that was appreciated in a way movies and had never been before. It seems like it was originally supposed to be like a night at a formal theatrical event rather than a casual night at the movies.