Complex sentence: The role of Dr. Hannibal Lecter was originally to be played by Gene Hackman, who also wished to direct; but he later withdrew from the project owing to the evolving screenplay's graphic content.
Split into simpler sentences: The role of Dr. Hannibal Lecter was originally to be played by Gene Hackman, who also wished to direct. He later withdrew from the project owing to the evolving screenplay's graphic content.