Why does it say "Kol Asher Karahu"?
Vilna Gaon: They thought that when he came to the king and said to hang Mordechai, the king called Mordechai, and he answered, and the king saw that he is correct. Therefore the king ordered Haman to take Mordechai around; perhaps Mordechai will become second to the king, and not Haman! Haman answered Karahu - it is Mikreh (chance). I do not know from where this [grandeur] came to him.
Malbim citing Mahara: Haman thought that his family fears that Haman requested to hang Mordechai, and via the dispute the king learned that Haman spoke falsely about him, and therefore he ruled [that Haman must take Mordechai around]. If so, there is no solution. Haman gave them good news - this was mere Mikreh (chance). Perhaps later I will request to hang him and the king will agree, for Mordechai already received his reward. His Chachamim and counselors told him not to confront Mordechai, for he will not succeed.
Haman told "his wife Zeresh and all his friends", but "his Chachamim and Zeresh" responded!
Torah Temimah citing Megilah 16a: Anyone who says a matter of Chachmah, even a Nochri, is called a Chacham.
Vilna Gaon: They are called Chachamim, for they recognized that Mazal does not apply to Yisrael (refer to 6:13:3:2).
What is the significance of being "mi'Zera ha'Yehudim"?
Torah Temimah citing Megilah 16a: You can overcome him only if he is from other Shevatim, but not if he is from Yehudah, Binyamin, Efrayim or Menasheh. You cannot overcome Yehudah - he was blessed "your hand is on the neck of your enemies." You cannot overcome the other three - "in front of Efrayim, Binyamin and Menasheh, stir up Your might."
Vilna Gaon: Haman told them that [Mordechai's rise] is chance. They said, since he is a Yehudi, it is from Shamayim. There is no Mazal to Yisrael! Therefore, you cannot overcome him. They ascend to Shamayim, and can change Mazalos. You should hide the [gallows] pole and break it, and make Shalom with him. He said, it is chance; perhaps I will be able to hang him afterwards.
Malbim: Haman said that [Mordechai's rise] is chance. They said, since he is a Yehudi, Hashgachas Hashem hovers over him. It is not chance. Since you began to fall, this shows that Hashem desires them and put His eye on them for the good. You will not overcome him!
Why does it say "Nafol Tipol"?
Rashi citing Megilah 16a: They told him that Yisrael are likened to earth and to stars. When they descend, they are like earth (everyone tramples over them). When they rise, they rise to the stars (and no one can rule over them. Ha'Rif - after they fall, they immediately rise, therefore you will fall.)
Malbim: (a) You began to fall. No one made any efforts for this. You yourself began - you came to Sha'ar ha'Melech and gave your counsel. (b) You began to fall, and he did not. "Lefanav" teaches that you fell before him (he did not fall at all yet). This was Hashgachah, due to his prayer and fasting. Your only chance is to fall (be submissive) in front of him, until he becomes haughty and ceases his prayer and Teshuvah. Then you can overpower him. When he raises his hand in Tefilah, "v'Gavar Yisrael" (Shemos 17:11).
