1)
Why did Hashem harden their hearts, and cause that they not make Shalom?
1.
Radak #1: This was their punishment for their sin, just like Hashem hardened Pharaoh's heart. Malbim #1 - their measure of sin was full; they were worthy to be punished, and not worthy of grace.
2.
Radak #2: It was in order to destroy them, like Hashem commanded Moshe - "Eten b'Yedchem Es Yoshvei ha'Aretz", "Pen Yachti'u Oscha" (Shemos 23:11, 33); Malbim #2 - and "Lo Sechayeh Kol Neshamah" (Devarim 20:12).
2)
What is "Techinah"?
1.
Malbim: It is like Chaninah (grace); Radak - and mercy.
