Complex sentence: Yasuo Otsuka had left Toei Animation to join A Productions in order to work on the Lupin adaptation as working on Lupin would allow him to use his knowledge and lifelong interest in guns and transport in his animation.
Split into simpler sentences: Yasuo Otsuka had left Toei Animation to join A Productions in order to work on the Lupin adaptation. Working on Lupin would allow him to use his knowledge and lifelong interest in guns and transport in his animation.