You're mistranslating. "צַר" doesn't mean "tsar" but is, rather, the masculine form of the word "צָרָה", "co-wife", and thus means "co-husband". That is, Ester was pointing out to Achashverosh that not only was Haman the one who was plotting to kill Ester's people (see the context there), Haman also had shared a wife with Achashverosh, namely Vashti.
Achashverosh was not angered by the latter revelation, since he was, as we know, licentious himself. He was, however, angry about the attempt on Ester's co-nationals' lives, and stood up for a walk in the garden. When he returned to the party, the following verses tell us,
Haman was falling on the chaise longue that Esther was on.
Haman saw that it didn't bother Achashverosh that they had shared a previous wife, so decided to try the same with Ester. But
the king said, "Do you plan also to conquer the queen with me at home?"
and had him killed. You see, sharing a wife was no big deal for Achashverosh; what bothered him was sharing a home. He was not only licentious but inhospitable.