With the Frankish expansion curtailed by another Justinian level plague that primarily hits the city dwelling monotheists the more eastern peoples of Europe are on a much more even footing when they're next able to try.
Click to shrink.Basically, the Carolingian Renaissance doesn't really get off the ground and Persia experiences a Mazdakist peasant uprising that uproots the nobility that makes Persia a far harder nut to crack for the arabs, with the gruelling conflict leading them to call it a day and focus westwards instead but with the momentum already sapped they don't really get past Cyrenaica.
