John Gill Commentary Judges 2:20

"And the anger of Jehovah was kindled against Israel; and he said, Because this nation have transgressed my covenant which I commanded their fathers, and have not hearkened unto my voice;" — Judges 2:20 (ASV)

And the anger of the Lord was hot against Israel
As at first, so whenever they fell into idolatry; see (Judges 2:14) ;

and he said, because this people have transgressed my covenant which I
commanded their fathers ;
made at Sinai, in which they were enjoined to have no other gods before him:

and have not hearkened to my voice ;
in his commands, and particularly what related to his worship and against idolatry.