In his Sherashim, the Radak translates the word chafu as “fell,” as Haman was described before (Esther 6:12).
Targum and the Vilna Gaon translate chafu as “despondent or disappointed.”
The Ibn Ezra, however, sees the word as an active verb, meaning that somebody – in this case, Achashverosh’s servants – did this to him. This is due to their recognizing the king’s displeasure.
The Alshich explains that it was a Persian custom to cover the face of a capital offender.
In another example of mida kineged mida (“measure for measure”), the Me’am Loez cites an earlier verse (Esther 1:19) that this custom of covering was Haman’s own idea.
The Brisker Rav says that this detail was necessary because Charvona was at the end of the list of chamberlain advisers listed earlier (Esther 1:10), so he would have been too intimidated to speak against Haman earlier. With Haman’s face covered, he is able to speak, as he does in the next verse.
The Maharsha says that, as we shall see in the next answer, the party was meant to endear Achashverosh to Esther specifically for her to divulge her lineage. It was therefore named after her. The Me’am Loez reminds us that “Esther” also means “hidden,” and this feast was thus meant with the express purpose of her revealing her secret identity.
Also, the above-mentioned concern for the poor also makes this uniquely “Esther’s” party.
The Ben Ish Chai adds that this party demonstrated to the people conclusively that the icons of Vashti were down, and the king’s heart belonged wholly to Esther.
Rav Chadidah says this party was made by Achashverosh for Esther, as opposed to Vashti’s party, that she made for herself (1:9). Rav Chadidah points out that this proves a great affection the king had for his new bride.