The Adonis Love System was a manga. It told the story of the beautiful host, Lin Tang, who had accidentally transmigrated to a strange world and was bound to a love system. Her mission was to conquer the four male gods and return to the peak of her life. Lin Tang was faced with the strong desire to monopolize and the difficulty of increasing her favorability. This manga was still being serialized, and the author was God Entertainment. We don't know the specific plot and comments of the manga.
Maybe Duke is doing it to achieve a certain goal or to protect someone or something important. There could be multiple reasons behind his actions that are yet to be revealed in the manga.