What is the meaning of "Shiches Chachmasecha Al Yif'asecha"?
Rashi: You became haughty about Yif'asecha (your appearance).
Radak: You became haughty about your radiance. This corrupted your Chachmah, for a Chacham does not get haughty about this world.
Malbim: You became haughty about your beauty ? this ruined both your Chachmah, and the Divine manifestation that was on you. "Al" means 'in addition to', like "Al Olas ha'Tamid" (Bamidbar 28:10).
Why did Hashem cast him to the ground?
Malbim: This was his punishment in this world ? he will be cast in front of kings, and they will see his shame.
What is "l'Ra'avah Vach"?
Rashi: To look at your shame. L'Ra'avah is like li'R'iyah.
Radak #1: People will see in you [the opposite of what you were and what you thought (about yourself) amidst your great pride; they will be astounded about you]. Also Yonason translates so. L'Ra'avah is a full Makor (infinitive). There is a pronounced Vov in place of the last letter of the root (Hei). Its grammatical form is like "Le'ahavah" (Devarim 19:9).
Radak #2: Some say, they will disgrace you. This is like "Hemah Yabitu Yir'u Vi" (Tehilim 22:18), "Es Kol Gavo'ah Yir'eh 1 " (Iyov 41:26).
Radak: There is no need to explain these expressions of Re'iyah unlike the context (seeing).