They did not - theirs was a very static and stable empire.
Cyrus did not defeat the Persians. Cyrus, as a Persian himself, actually gave them an empire.
Aryans were the fierce nomadic herders that conquered them.
Gaining an empire is its own reward.
The Persians absorbed the Phoenicians into their empire, and used their resources.
Persians
No.
The Persians
Alexander the Great conquered the Persian Empire and converted it into an empire of his own, not to destroy the Persians but to convert them to Greek culture.
The Persians conquered the Babylonian Empire in 539 BCE.
He was not mean to the Persians - he led them to form the greatest empire of the time.
An empire.
It expanded the Persians.