Why did Cyrus the Great want to conquer so much?

Answer 1

Part ambition, part a rational desire to bring good government and prosperity, and part being that onece you statr the conquest activity, there it is difficult to stop without getting caught in a backlash.

The Persians were a tribe in the land east of what we now call the Persian Gulf. They were subservient to the Medes. Cyrus reversed this and used the combined strength of Media and Persia to overcome the Babylonian Empire. This left border problems to the east and west so he continued subduing these threats and opportunities until his death in the wars.

His son Cambyses took on Egypt and Libya, and successor Darius the Great stabilised the empire, adding small areas just to form defensible borders.

Answer 2

Cyrus the Great conquered other territories because he had the power to do so.

Historically, there was the "Right to Conquest" which was a pervasive idea in political thought. The idea was that it was natural for any country or state to grow and control more territory as it grew stronger. This allowed weaker states to dissolve in place of ones that were better run, a bureaucratic version of "survival of the fittest". The "Right to Conquest" prevailed as the dominant theory of nation-building until the mid-1800s when people started bringing up the concept of self-sovereignty and ethnic nationalism, which held the idea that people should govern themselves even if they are not the most powerful in the world. This view of state sovereignty has become dominant today and the Right to Conquest is seen as incorrect.

Since the Cyrus the Great lived well within the Right to Conquest Period, he did not have to assert a reason to conquer neighboring territories in Southwest Asia. It was his natural prerogative.