וַיַּנַּ֤ח יְהוָה֙ אֶת־הַגּוֹיִ֣ם הָאֵ֔לֶּה לְבִלְתִּ֥י הוֹרִישָׁ֖ם מַהֵ֑ר וְלֹ֥א נְתָנָ֖ם בְּיַד־יְהוֹשֻֽׁעַ׃ (פ)
און גאָט האָט געלאָזט די דאָזיקע פֿעלקער, זײ ניט צו פֿאַרטרײַבן אױףֿ גיך; און ער האָט זײ ניט געגעבן אין דער האַנט פֿון יהושוען.
Metzudat David
AND HE (HASHEM) LEFT: Because of this, Hashem chose this as the punishment and He left these nation, that are listed below
Metzudat David
...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