Complex sentence: Lasseter was fired from Disney in 1983 for pushing the studio to explore computer animation production, going on to become the creative head of Pixar, a pioneering computer animation studio that would begin a close association with Disney in the late 1980s.
Split into simpler sentences: Lasseter was fired from Disney in 1983 for pushing the studio to explore computer animation production. He went on to become the creative head of Pixar, a pioneering computer animation studio that would begin a close association with Disney in the late 1980s.