Judges 1:30
Neither did Zebulun drive out the inhabitants of Kitron, nor the inhabitants of Nahalol; but the Canaanites dwelt among them, and became tributaries. Neither did Zebulun drive out the inhabitants of Kitron, nor the inhabitants of Nahalol; but the Canaanites dwelt among them, and became tributaries.
Zebulun failed to expel the inhabitants of Kitron and Nahalol, so the Canaanites continued to dwell among the Israelites. This was part of Israel's larger failure to fully carry out God's command to dispossess the inhabitants of the land. The people followed God's plan only partly, choosing convenience instead of complete obedience. By leaving those inhabitants in place, they left among themselves a people who could become a snare to them.