“Hitherto, except in exploration fantasies, the fantastic element was brought in by magic… but by the end of the last century it had become difficult to squeeze even a momentary belief out of magic any longer. It occurred to me that instead of the usual interview with the devil or a magician, an ingenious use of scientific patter might with advantage be substituted… I simply brought the fetish up to date, and made it as near actual theory as possible.”
— H.G. Wells
Wells claims that he had a notion to paint the old tropes of fantasy with a new, scientific veneer, without substantively changing them, and this sidestep is where science fiction emerged from fantasy. Not an auspicious birth. Feels about right, though; SF always seemed to be a flavor of fantasy.