They were never supernatural. They were just not known or not understood. Physics is by some definition the study of the natural world. There is a lot we don't know about the natural world, but what we know and don't know aren't what make something "supernatural".
Any sufficiently advanced technology is indistinguishable from magic. - Arthur C. Clarke
LEDs were absolutely supernatural. As I said, go back in time with one and show it to Medieval serfs and see what they say. Supernatural is anything that you can't explain given your understanding of the universe.
