Andalusia was ruled by both Arabs and amazighs and one of the reasons it fell is ethnic conflicts between the amazigh and the arabs
It's simply because the ummyads had employed arab superiority, even though much of the bulk of the army invading spain was indeed of berber origin. They still looked down upon them as second class citizens, even when berbers indeed did convert they still forced to pay jizya to the arabs for example.
The Arabs never originally intended for berbers to convert, merely as a way to extract revenue. Coupled with the fact that berbers revolted and kicked out ummyad rulers and what not lead to these ethnic conflicts. They founded their own kingdoms and states, one of the first to do so of non arab origin.
The Almohads and Almoravids, pretty much stopped christian spain for making any more advances, without that pivtol role. Al Andalus would have likely stopped a few centuries earlier.
I'd say, the abbasids were much better in this regard as they were heavily influenced by persians culture and thought especially considering their geography. Although in the later years, they merely were figureheads for different turkic populations.
What is the most intriguing, is after the abbasids and later fatamids turkic populations and turks pretty much dominated the islamic world. Malmuks, for example being an earlier example. Seljuks, who defended the holy cities from the first crusades.
It was the century of turks pretty much, although muslims lost al andalus they gained anatolia and from then on much of the balkans until recent history.