What is the significance of Haman's 10 sons?
Rashi: They wrote accusations against Yehudah and Yerushalayim - "uv'Malchus Achashverosh bi'Schilas Malchuso Kasvu Sitnah Al Yosheveu Yehudah vi'Yrushalayim" (Ezra 4:6). They wrote to stop Jews from ascending from Galus to build the Beis ha'Mikdash which began in the days of Koresh. The Kusim slandered them and made them cease. After Koresh died, Achashverosh became king and Haman was elevated. He was concerned lest they engage in building; [his sons] sent in the name of Achashverosh to the Sarim to stop them.
Vilna Gaon: Their names correspond to the 10 names of idolatry. The 10th encompasses all of them; therefore the 'Vov' of "Vayzasa" is elongated. Haman and his sons correspond to the 11 curses 1 in the Torah (Devarim 27:15-25).
Rashi (Devarim 27:24) says that there are 11. Bartenura - he does not count the last ("Arur Asher Lo Yakim ... "). It is for the entire Torah, and not for a particular Aveirah.
Why did they not take the spoils?
Rashi (8:11): They showed everyone that it was not for the sake of money. Vilna Gaon - rather, it was in order to fulfill the kingdom's command 1 !
Manos ha'Levi: This established the Jews to hate unjust gain. Even though the decree was to take the spoils, they refrained!
Also taking the spoils was part of the decree! Perhaps it was understood that it is Reshus, and not obligatory. (PF)
