Why did he say ask "Mah Na'asah Yekar u'Gedulah"?
Vilna Gaon: He realized that there is a great claim [for Mordechai]. He asked about what Yekar (honor) and Gedulah (wealth) was given already.
Malbim: There should have been honor at the time, to publicize that he acted to save the king from death. There should have been grandeur afterwards, to elevate him above all the Sarim. Even though he knew that he was aggrandized to sit in Sha'ar ha'Melech, that was because he raised Esther, and not "Al Zeh" (due to saving the king).
Why did they say "Lo Na'aseh Imo Davar"?
Torah Temimah citing Megilah 16a: They said so out of hate for Haman, not out of love for Mordechai 1 .
Maharsha (16a): They should have answered the king like his words - 'no honor and grandeur was done for him.' They omitted this, for they did not love Mordechai (they did not want him to get honor or grandeur). They said "Davar", that the king should do for him a matter not of honor and grandeur, amidst hatred of Haman.
