Commentary for Judges 2:23

AND HE (HASHEM) LEFT: Because of this, Hashem chose this as the punishment and He left these nation, that are listed below

...WITHOUT EXPELLING THEM QUICKLY: It wants to teach that in His wisdom he decreed not to expel them quickly, rather very slowly, and to "not immediately hand them over to Joshua." And Because of the punishment "in order to test them" He let them be all over, and He did not continue to expel a person from now on