Covering every rooth with solar panels is quite literally impossible. Wind energy is also horrible for the environment as when ever it gets too windy, it has to be shut off or it's motor will combust. That ain't even the main issue, it's the fact it's killing thousands of endangered birds every year, and tens of thousands of non endangered birds. Solar has also been killing birds that fly over the solar farms, getting fried by the intensified sunlight reflected off of panels.

My theory is because of magic, scientists of then times could turn their eyes into microscopes and because of this, they discovered bacteria, mold spores, viruses, etc giving them germ theory centuries before it was discovered in our time.