I believe myopia is primarily caused by less use of the eyes to focus on a variety of distances and scenes. We mostly are indoors looking at books and now screens -> myopia goes way up. I also believe it can be reversed by using the eyes differently and this happened for me.

I had myopia from when I was a teenager. I didn't realize it till I was 21 and tried glasses and could suddenly see what I didn't know was possible to see. I then wore glasses from 21 to 27. Quit wearing glasses at 27 and left the office and computer to be mostly full time in the woods. Two years later my myopia had mostly reversed and I could see crisp detail at long distances without glasses for the first time. Six years now since I noticed the reversal and I still can see clearly at long distances. I love it.