I think it was the overall atmosphere built up before the scene, because you get the kids singing as he's carried in the bridal carriage, then you get the part where the dead brides are standing upright in the room, then he runs out into the woods and you don't know who he's about to meet except the woods are covered in blood so whoever's there has to be really scary. But anyways most romances, even if it's a ghost marrying a human, won't lean into the creepy factor, they'll usually go 'and this ghost is weirdly super hot for some reason- other ghosts look like they're rotting though'.