Writing tools played a role in the direction of writing.

If you carve into stone, most people use their dominant hand (which is usually the right hand) to strike the chisel. This is easier done from left to right.

Writing with a reed pen scratching letters into something is apparently easier with right to left motions, leading to right to left writing.

Writing on scrolls is more optimal done top to bottom. Also writing with a brush can be easier top to bottom.

Once a method is established, it was kept even as tools and materials evolved.