1)
Having seen how every word of Moshe transpired, how could anyone be so foolish as to ignore his warning concerning the plague of hail?
1.
Oznayim la'Torah #1: Because they simply could not bring themselves to believe that Moshe would offer them good advice - and assumed that he must have some trick or other up his sleeve.
2.
Oznayim la'Torah #2: Because, just as Hashem hardened Pharaoh's heart, so too, did He harden the hearts of his servants, rendering them unable to grasp the truth.
