The decree states the need for peace and tranquility (Greek text only)

“I have become the ruler of many nations and the master of the whole world. I am not elated with the presumption of authority but I always act reasonably and with kindness. I have determined to settle the lives of my subjects in lasting tranquility in order to make my kingdom peaceable and open to travel throughout all its extent. I want to restore the peace desired by all men.”

Once again, this whole decree only appears in the Greek text and not in the Hebrew text at all. The king said that he was the ruler of many nations. He is the master of the whole world that is their known civilized world at that time. It was not his presumption of authority, but he was trying to act reasonably with kindness. He wanted everyone to live in tranquility with easy access to travel. He wanted peace.