- Mordecai was the lone Jew in the king's gate. Mordecai job was to represent the Jews and translate the king's order for the Jewish community.
Mordecai said that he does not bow because he is Jewish.
Haman wanted to kill Mordecai and end the disobedience, but could not ask the king to kill Mordecai because the king did not make the order that the leaders at the king's gate must bow. Killing Mordecai would not solve Haman's problem because a new Jewish representative will take his place and will not bow.
So Haman decided to kill the whole nation of Mordecai and Mordecai himself, and then there will be no need for a new Jewish representative, who might not bow to him.
- Jewish Masscre by Haman