> Still, the end of Mesopotamian records is abrupt. There's a written record from prehistory until the wars of around 700 BC, where the use of writing drops off but doesn't completely stop. But written records in Akkadian, the education of priests and scribes in Akkadian and Sumerian (itself dead for 2000 years by then as a purely liturgical language) basically stops after the fall of Babylon in 539 BC.

This probably isn't so much a move away from the use of writing, but a shift away from Akkadian cuneiform on clay tablets to Aramaic on vellum. Clay tablets, even unfired, survive a long time. Vellum doesn't in that climate.