Montaigne's Cat adds an important element:
One further point — they systematically destroyed the traces of the pre-Islamic cultures they conquered. Some texts were translated into Arabic, but the originals were destroyed. This is like a thief covering his tracks. Thus they could claim originality, and never have to face the fact of their secondarity or inferiority. This is exactly the opposite of the Western impulse of preservation. By preserving texts and artifacts and artworks, the West can always return to the original to deepen its understanding. It is why the history of the West can be seen as a nearly continuous series of Renaissances, and the history of Islam as one of deepening decline and stagnation.
which gave a decisive check to the career of Arab conquest in Western Europe... Gibbon devotes several pages of his great work to the narrative of the battle of Tours, and to the consideration of the consequences which probably would have resulted if Abderrahman's enterprise had not been crushed by the Frankish chief. Schlegel speaks of thismighty victoryin terms of fervent gratitude, and tells howthe arm of Charles Martel saved and delivered the Christian nations of the West from the deadly grasp of all-destroying Islam.
The Muslims desired to learn the sciences of the foreign nations. They made them their own through translations. They pressed them into the mold of their own views. They peeled off these strange tongues and made them pass into their own idiom. The manuscripts in the non-Arabic languages were forgotten, abandoned, and scattered. Thus students of the sciences needed a knowledge of the meaning of Arabic words and Arabic writing. They could dispense with all other languages, because they had been wiped out and there was no longer any interest in them.[via Montaigne's Cat at lgf]