Seeing as, when Yisrael do the will of Hakadosh-Baruch-Hu, the wild beasts will do them no harm (See Iyov, 5:53), why does the Torah inform them that they will not be able to destroy the Cana'ani nations quickly ? in case the wild beasts multiply?
Rashi: Moshe 1 is predicting here that Yisrael will sin, rendering them unworthy of the miracle 2 that wild beasts will not harm them (when they come to devour the carcasses of the slain - Targum Yonasan).
Like he predicted that they will be exiled. Refer to Devarim 4:25:2:1*.
Ramban: See Vayikra 26:6.
If, as the following Pasuk relates, Hashem will destroy the nations - in spite of Yisrael having sinned, why will He not also destroy the wild beasts?
Oznayim la'Torah: Because, whereas the Cana'anim were far more wicked than Yisrael and deserved to be destroyed, the wild animals, whose actions are governed by instinct and who are therefore not considered wicked, did not.
QUESTIONS ON RASHI
Rashi writes that Yisrael will sin, and not merit that wild beasts not harm them. Why are we not then afraid that the remaining Cana'anim will be able to harm them?