Complex sentence: Because of his success as the director of "Dracula" he was given a considerable leeway for a major studio's first horror film, this and the fact he was working in Pre-Code Hollywood enabled a unique production.
Split into simpler sentences: Because of his success as the director of "Dracula" he was given a considerable leeway for a major studio's first horror film. This and the fact that he was working in Pre-Code Hollywood enabled a unique production.