Summary: After Joshua’s death, Judah is appointed by God as leader of the Jewish people to continue the military conquest of Canaan. His brother Simeon joined him and they completed a number of successful battles including the capture of Jerusalem and Hebron. Nevertheless, the last part of the chapter (verses 21-36) describe several occasions where individual tribes failed to drive out their enemies from the land completely.
A deeper look: The Midrash (Exodus Rabbah 27:8) explains that the father-in-law of Moses had seven names including Yitro (Jethro), for a section of Torah was added (yeter) in his merit, and Keni from whom the Kenites are descended (see Judges 1:16). The Midrash explains that the name Keni implies that he was a zealot (kanoh) for heaven and Torah which is why he abandoned idol worship and embraced monotheism (Mechilta of Rebbi Yishmael on Yitro).
Rabbi David Kimchi (d. 1235) explained that the Jewish people remembered the good Yitro had done and took care of his descendants the Kenites by settling them away from battle in the pastures around the city of Jericho, fulfilling the promise made by Moses to Chovav, the son of Yitro (Numbers 10:29).
Rabbi Moshe Dovid Valle (d. 1777) further explained that there is a deeper, earlier connection in the name Keni originating with Kain, the brother of Abel and son of Adam and Eve (Ohr Zarua on Judges 1:16). When Bilaam blessed the Jewish people (Numbers 24:21-22) he perceived the greatness of the Kenites saying ‘How firm is your dwelling place … For if Kain is laid waste, how far will Assyria take you captive?’ Rashi (d. 1105) comments that the Kenites were fortunate to be settled for even though they were destined to be exiled with the Ten Tribes of Israel (see Kings I 11:31), unlike their ancestor Kain they would never be banished completely (Rashi on Numbers 24:22, Genesis 4:12).
While the Kenites were righteous, they had had no direct connection with the Jewish people. This changed after the Jewish people settled in the Land of Israel. The Kenites were also granted land and now, having been spiritual wanderers for so long, were spiritually elevated through their own inheritance.