i think pops up in early computer rpgs like ultima a lot because the original Dungeons and Dragons was full of that kind of anachronistic stuff. TSR probably didn’t intentionally make it post-apocalypse though. they were just cramming whatever they thought was cool at the moment into their game, which is why you’re just as likely to find a downed spaceship as a dinosaur in Blackmoore. the post-apocalypse angle probably game to be when early crpgs wanted to ape that but wanted give it a proper story justification

i’ve also heard people say that the silmarillion has scifi elements, but i’m not sure how much of that is what tolkien intended versus what people read into it. i’ve also heard that the trope originates from medieval people coming across ruins of ancient roman architecture, but no examples were given- although it’s funny to think we have robots in The Legend of Zelda because aquaducts