Could you imagine how frustrated Haman would have been had he known that Mordecai would replace him at the kings right hand? (I often think the Lord must enjoy irony!)
Isn't amazing how He works. Esther had been just a stranger in a foreign land a mere few chapters ago, and now, she is queen of the most powerful nation in the world. She had been marked for death, but now, the man who sought her life and the life of her people was dead, and she was the master of his estate.
Mordecai sat at the gate of the king, but now he would sit at his side, and was placed as steward of the former estate of the man who sought his ruin above anything else.