As I hope my earlier time line pointed out, I think that the search for a moral or psychological cause for Islam's decline is foolish. Beside such searches tend to just be ways of having Europeans feel good about themselves (OOO, we aren't backward, fatalistic, and stupid like them). The decline was political (lack of a stable system following the Turkish influx, not necessarily a centralized empire, but even stable states would have been adequate), military (Mongol assaults on the core area), and economic (more to follow).
The economic needs a bit more explanation. Muslim states have generally been, even today, trapped in an agarian regime. Wealth is derived from land ownership (not just agriculture but mineral extraction as well), taxation, and control of known trade routes. Technology remains stable, though slow innovation is common enough. When the Italians developed capital investment (improved by northern Europeans a century later) the rules of the international game of wealth and power changed. No other society realized this until very late (with the exception of Japan, the 20th Century only).
The benefits of this transformation weren't immediately obvious because of Europe's initial backwardness and the resources available to early modern Muslim empires (Mamlukes, Ottomans, Persians, Mughals etc.). But as time went on, the Europeans were on perpetual motion, while the Muslims empires were facing the standard limit of an agarian empire/dynasty (roughly 2 centuries). Actually the Morrocans, Ottomans, and Safavids/Pahlavis did better than most in the face of European challenges. The Mughals and Marathas fell apart after a century or less (depending on when you start). The Manchus collapsed 70 years after the Opium War, their first introduction to a European spanking.