Why was the death of darius important to alexander's conquest of persia?

Darius was the Persian king; it was necessary for Alexander to remove the Persian head so that he  could rule over the Persian body.

Explanation:

a punishment or the threat of punishment used to enforce conformity. enforcement of norms or shared rules of conduct that tell people how to act in specific situations. social control. not everyone internalizes all of society's norms, and some people must be motivated by self-fulfillment.