Complex sentence: During his tenure, he helped Fox become a major player in the world of animated feature films, and in 1998 he led Fox's acquisition of fledgling visual effects/commercial house Blue Sky Studios, which he built into a successful producer of animated features.
Split into simpler sentences: During his tenure, he produced and helped Fox become a major player in the world of animated feature films. In 1998 he led Fox's acquisition of fledgling visual effects/commercial house Blue Sky Studios, which he built into a successful producer of animated features.