1)
What is the meaning of "Ki Tach me'Re'os"?
1.
Radak #1: Their eyes are plastered shut.
2.
Radak #2: This is Po'el Yotzei (it acts on others); Kel plastered their eyes. This is like "Hashmen Lev ha'Am ha'Zeh" (6:10). Alternatively, their Yetzer ha'Ra was Tach and overpowered their intellect.
3.
Malbim: It is not astounding that they do not understand the folly of their belief. One who is blind cannot see physical things. If one's heart is plastered, he cannot understand.