Most of Islamic science was destroyed by the Mongol invasion. The economic destruction was widespread at the same time, comparable to that of the South during the Civil War or that wrought by WWII. Additionally, Islamic society turned more conservative and fundamentalist as a response to the Mongols. (Sort of a "God is punishing us so lets get conservative" view.) Currently, Islamic philosophy is mostly fundamentalist conservative and very anti-science, particularly anti-evolutionary theory.
Have you ever read Louis L'Amour's "Walking Drum". I highly recommend it. It is a book set in the peak of the Muslim rule in Southern Europe and Northern Africa.