Is myopia always caused by increased axial length?
You’re on the right track, but it’s not the thickness of the cornea but the front curve of the cornea in relation to the length of the eyeball that determines the degree of myopia. The steeper the curve the shorter the focal distance. If the front curve of the cornea is too steep and it focuses light before it reaches the retina at the back of the eye you have myopia, and the steeper the curve the more myopia you will have. That’s the same as saying if the eyeball is too long for the cornea the light again will focus before it reaches the retina and you have myopia, and the longer the eyeball the more myopia you will have.
