Why did islam survive successive invasions by steppe peoples (turks and mongols) from 945 on?

In 945, Ahmad Ibn Buya, from the Buyid Dynasty, conquered Iraq and made Baghdad its capital, receiving the title of "Fortifier of the State". They are thought not to be descendants of Ali (Original Muslim Prophet). However, they rarely enforced their religious views on the territories they ruled. This ensured the continuity of practices in Muslim faith during this period. This dynasty's rule encompassed the territory of what is modern day Iraq, Iran, Kuwait, Syria, and parts of Oman, UAE, and Afghanistan. All of these countries with a majority of Muslim population.