C. F. Keil and Franz Delitzsch on Judges 2:20-21

Jdg 2:20-21 Chastisement of the Rebellious Nation. - Jdg 2:20, Jdg 2:21. On account of this idolatry, which was not only constantly repeated, but continued to grow worse and worse, the anger of the Lord burned so fiercely against Israel, that He determined to destroy no more of the nations which Joshua had left when he died, before the people that had broken His covenant. In order to set forth this divine purpose most distinctly, it is thrown into the form of a sentence uttered by God through the expression וגו ויּאמר. The Lord said, “Because this people has transgressed my covenant, ... I also will no longer keep my covenant promise (Exo 23:23, Exo 23:27., Exo 34:10.), and will no more drive out any of the remaining Canaanites before them” (see Jos 23:13).