Light pollution is just one of the by-products of industrialization. Fifteen-hundred years ago the air was a lot cleaner, hence more transparent which means more starlight/moonlight reaches the surface at night, than it is today -less soot, smoke, dirt, suspended aerosols, smog- so much so it is estimated, that the light from the stars alone would have enough to read a newspaper by -had newspapers existed then. If we want to see the sky as Galileo saw it, we're going to need more than just turning off the lights to do so.