It is known that the Islamic civilization was a frontier for scientific education back then. How did it decline? Did Al ghazali had anything to do with it? How about today's contribution of muslims to the science? Is is that bad, or have they recovered?
One of the many reasons for the decline of the Islamic civilisation, and the end of of the Islamic Golden Age was the Mongol invasion, and especially the Sack of Baghdad (1258) that resulted in the annihilation of the caliphatic bureaucracy (including Caliph himself), administration, death of countless scholars, librarians and philosophers, and the destruction of the Grand Library of Baghdad (House of Wisdom,Arabic: بيت الحكمة; Bayt al-Hikma), which was the hub of all scientific knowledge of the Islamic world.
(source: Saunders, J.J. 2001. "The History of the Mongol Conquests.")
The Grand Library was not just a library, but a magnificient academic institute that employed nearly all the greatest minds of the Caliphate; not just Muslims, but also Christians, Jews and Zoroastrians. It also housed unique copies of ancient and medieval texts partaining to math, science, medicine and law, as well as copies of the works of Aristotle and Plato. Its destruction, and massacre of the scholars could be considered a "decapitation" of the Islamic culture (personally I would compare it what would happen if the Internet was suddenly and irreversibly destroyed). To better imagine the scale of the destruction, remember that the Sack of Baghdad mostly predates print, so the number of existing books was relatively small; many important volumes existed in only 1, or 2 copies. Mongols destroyed so many books and scrolls (by dumping them into river Tigris) that the river "ran black with ink" for days.
(source: W. Wager Cooper, Piyu Yue (2008), ''Challenges of the Muslim world: present, future and past'')
What remained of the might of the Islamic culture was further destabilized by Catholic powers challenging Muslim rule, as well as the concept of taqleed (Arabic تَقْليد taqlīd), "imiatiation" of the fundamentals of the faith instead of Ijtihad (Arabic: اجتهاد ijtihād, "diligence") requiring Muslims to use critical thinking in matters of faith or science, and separation fo the two. Taqleed led to the triumph of the literal interpretation of Quran by the judges faih, and mujahid (teachers/gurus) rather than rational, critical analisis by scholar-theologians. It could be said to be the start of Islamic fundamentalism, adn anti-intellectualism.
(source: Esposito, J. "In the Islamic World: Past and Present")