Final answer:
The rise of the Persian Empire was influenced by its policy of allowing conquered peoples to maintain their customs and religious beliefs, supported by a degree of religious tolerance built into the imperial system.
Step-by-step explanation:
One cause of the rise of the Persian Empire was its policy of respecting the customs and religious beliefs of the people they conquered. This tolerance allowed the Persians to maintain stability within their diverse empire, which spanned a vast number of ethnic groups and religions.
The approach was a significant shift from previous empires that had enforced cultural assimilation and religious conversion.
The foundation of Zoroastrianism as the state religion also played a role, as it encouraged the vision of the Persian kings as the representatives of Ahura Mazda, pushing forth the idea of a battle between good and evil, and sometimes helping justify imperial ambitions.