Why does it say "Ki Yimatzei"?
Rashi citing Targum Yonasan: It is like the shame of a thief when he is first caught, and until now he was established to be trustworthy. Radak - a known thief is not ashamed when he is caught.
Malbim: An [intrinsic] thief who is found, his shame is not due to the act itself, rather, because he is found, and his evil is revealed to all. One who sins by chance [in order to get a benefit], he regrets the sin itself; one who intrinsically wants to sin does not. A parable for this is a harlot who is Mezanah for money. If she is stripped naked and did not get her food and drink, she regrets the deed itself. One who desires Zenus itself does not regret the Zenus, only what occurred to her. Had Yisrael served idolatry for expected benefit, they would regret their deeds when they see that they got only evil and afflictions. Bnei Yisrael were like the [intrinsic] thief; they are not ashamed about the act itself, only for being found.
What is the meaning of "Ken Hovishu"?
Radak: They should have been ashamed - but they had no shame. If they had shame, they would repent. They should have been ashamed, for Hashem chose them and their fathers, and they strayed after other gods. In the parable, they are like one who was established to be trustworthy, and he is caught stealing. So Yisrael were established to be Am Hashem, who do His Mitzvos and cling to Him, and they went to serve idolatry. They should have been ashamed for leaving their Chazakah!
Malbim: Their shame was only for the results of their evil, but not for the evil path itself. "Teyaserech Ra'asech" (verse 19) is a command. Regret the evil itself, and not only the punishment that comes for it!
Why is there no prefix Vov before "Sareihem"?
Radak: We find like this - "Shemesh Yare'ach" (Chabakuk 3:11), "Reuven Shimon" (Shemos 1:2) and similar verses.
Who are the Kohanim?
Radak: They are Kohanim of the Ba'al.
Who are the Nevi'im?
Radak: They are the false Nevi'im.
