@vikorr,
Oops...I meant the Mongols not Huns. Yes they expanded, but expanding brings new enemies with each expansion. When you start off fighting for survival it is hard to know when to stop.
Their immediate neighbour was Byzantium and they conflicted for the same lands. There were the Crusades, the Reconquistadora of Spain and the Mongol invasion. All of these were very unpleasant for any Muslim to try to live through. By comparison, they were relatively polite in conquering Christian and Pagan lands, taxing people till they converted. It was Vlad Dracula who impaled 10,000 Muslim soldiers to shock them into turning around. It was the Crusaders who massacred Jews and Muslims after they laid their weapons aside. It was the Christian Spanish who gave true meaning to the word Inquisition, with a policy of killing any Jews or Muslims who didn't leave or convert, though many who converted were later suspect and killed anyway. It was the pagan Mongols who devastated Muslim lands in a manner that is still talked about today in Muslim cafes.
Whilst others were trying to exterminate them, they welcomed academics to their universities, something that was to help kickstart the renaissance.
In an age of conquest, Muslims were the polite ones.