Complex sentence: It was the first film to break away from the Disney-esque mold of Toei animation at the time of its production; because of this, it is considered by some to be the first film in the contemporary anime style.
Split into simpler sentences: It was the first film to really break away from the Disney-esque mold of Toei animation at the time of its production. And because of this it is considered by some to be the first film in the Contemporary anime style.