Mordecai refused to bow to Haman because Haman's honor had become more than ordinary court respect in the story. Esther presents the refusal as a public act that exposes Haman's pride and turns his anger against all the Jews in the empire.
The scene comes after Haman is promoted above the other officials. The king's servants bow, but Mordecai does not. The text does not pause to explain every motive, but it does connect Mordecai's refusal with his Jewish identity and with Haman's violent response. The point is not private stubbornness; it is the moment when hidden identity becomes public danger.
This question helps readers see how Esther moves from palace politics to covenant-risk. A single conflict at the gate becomes the doorway into the larger threat against God's people.
2All the king`s servants, who were in the king`s gate, bowed down, and did reverence to Haman; for the king had so commanded concerning him. But Mordecai didn`t bow down, nor did him reverence.