That’s quite a question. It seems silly in one way: porn is always around. And silly in another way: later European art is full of nudity and depictions of mythological sex and rape scenes. Yet the question doesn’t seem entirely silly.
Lawrence Alma-Tadema wasn't the only Victorian-era painter to use ancient backdrops for his paintings as a cover for nudity. In France, William-Adolphe Bouguereau didn't even bother with classical settings.