1)
What is the meaning of "Ki Lo Lehorish"?
1.
Rashi citing Targum Yonasan: After they sinned, they could not dispossess the residents of the plain.
2.
Radak: Even though Hashem was with Yehudah, they could not dispossess them, for "Hashem left them to test Yisrael" (3:1).
3.
Malbim: They did not conquer the mountain with intent to conquer the plain afterwards, even though [normally] this is easy - "Ki Har Yihyeh Lecha? Torish Es Ha'Emek" (Yehoshua 17:18). Here they slackened and feared to do so, because the residents of the plain had iron chariots.
