Meaning: "I once bought the assests and thought, why not use them? I'll figure something out later."
Just kidding. I hate the fact that people think sci-fi and fantasy are mutually exclusive. Both are a big sandbox, so why not use them both? One of my all time favourite graphic novel series is Thorgall, the tale of a man, raised in a viking village, who finds out in the first two issues that thousands of years before, the Antlanteans left Earth to find a new planet to live on, and send back an exploration mission to bring back resources and that he's the son of two crewmembers and one of the few survivors after their spaceship was destroyed. So, just when you think "oh, it's sci-fi", next issue, he's facing off witches and wizards. In one of the later issues, he even sneaks into Asgard and ranks the top five of "things I want destroyed" of the mythical serpent Nydhogg. And why not? If it works, go with it.