> I wonder what the turning point was when people stopped thinking of electricity as magic and instead thought of it as science

Once they could make predictions and those predictions were verified by reality. "When I flip this switch the light will turn on.....When I move this magnet past this wire I can shock my lab assistant...."

I don't know much about D&D but I would venture the guess that electrons are far stranger than mana. I mean, not only do they have a wavelength[0], you can do the Double Slit experiment with them[1], but they also have an intrinsic angular momentum and there are rules of which electron can be where based on this "spin"[2]. That's just for starters.

Calling them "mana" (whatever that is) might not be any more wrong than calling them particles.

0 - https://en.wikipedia.org/wiki/Matter_wave 1 - https://en.wikipedia.org/wiki/Double-slit_experiment 2 - https://en.wikipedia.org/wiki/Spin_%28physics%29