I'm no expert but from what I've gleaned from various articles around the web and some recent questions to my optician is that myopia is caused by how light rays focus inside our eyes. Rays that don't focus correctly at the back of the eye (perhaps outside the macula?) create a feedback loop that causes the eye to grow longer. Unfortunately there's no opposite effect to make the eye shorter. So naturally there's a predisposition for everyone to become short sighted with this mechanism (perhaps a primary cause of coronavision?):

"It is believed that the trigger for the eye to continue growing beyond its optimal length is in the way rays of light entering the visual system are focused on the back of the eye. In myopia, these rays or images focus in front of the retina causing a blurred image. Spectacles or contact lenses for myopia help focus these rays of light directly onto the retina in the central area correcting the vision, however, in the peripheral areas of the eye the rays of light are focused on theory “behind” the retina. It is believed this is a stimulus for the eye to grow. Myopia control or myopia management spectacles lenses and contact lenses are designed with more than one point of focus and therefore diminish this stimulus for the eye to grow."

Above quoted from:

https://www.openaccessgovernment.org/myopia-management-looki...