First, Islam conquered the wealthy, culturally rich empires that once ruled over the region. This started a slow process of stagnation and decay. Things were still okay for a few centuries because virtually all trade with Asia and its wondrous silks and porcelains and spices had to go through the Middle East, so Islamic caliphates were able to skim off the top of the lucrative silk road trade. Until...
The mongols empire annihilated all those comfy Islamic trading posts when it swept over Asia. The damage here was both economic and cultural, because the Mongols burned a shit ton of libraries and cities destroying all the ancient culture the Islamic scholars had been studying and preserving (because they didn't really create much themselves). The Mongols did restore trade eventually, but with significantly fewer Arabic middle men involved, the mideast were reduced to Mongol vassals and client states for a few centuries. It wouldn't be until the Ottoman Turks took over the region, after the Mongol conquests, that Islamic dominance over European-Asian trade would be restored, unfortunately, it would be just in time for...
Europeans discovering alternate sea routes to Asia. Now nobody had a reason to trade with the Ottomans, they could get to India, China, etc by ocean. As both Eastern and Western passages to Asia were discovered, the Ottoman Empire's importance as the arbiter of East-West trade diminished further and further. They managed to hang on for a while because they also controlled the eastern Mediterranean and the Red Sea, but Europeans just went all-in on using the Atlantic to skirt around South America and Africa.
So you had a region in the grips of a culturally backward religion which stifled creative expression and scientific advancement, an apocalyptic steppe nigger chimpout that depopulated whole kingdoms and destroyed priceless stores of knowledge, and then the loss of its prized position at the cross roads of transcontinental trade.