Why does it say "va'Ashalchehu"?
Radak: I ceased to guard them; I made them Hefker for nations to send their hands against them.
Malbim: I sent them from My face, and removed My Hashgachah from them.
What is "bi'Shrirus Libam"?
Rashi: In the vision of their hearts (their desires). This is like "Lema'an Shorerai" (5:9).
Radak: It is the strength of their evil hearts. They did not want to repent from their evil.
Why does it say "Yelechu b'Mo'atzoseihem"?
Radak: Just like they counseled evil for themselves, so they will go in evil, and perish.
Malbim: Even though I removed My Hashgachah from them, and rain of Hashgachah did not fall in its time, they went in their evil intents.