The most accurate summary of the expansion of the Muslim Empires through the lens of cause and effect is:
Cause: Leadership changes and military conquest
Effect: The Umayyad Caliphate expanded to Syria and centralized Islamic power.
Cause: Political revolts
Effect: The Abbasid Caliphate expanded to Iraq and developed socially and culturally.
This summary correctly outlines the key causes leading to the territorial expansions and notable developments of both the Umayyad and Abbasid Caliphates.