‘ Yet the children of Manasseh could not drive out the inhabitants of those cities, but the Canaanites would dwell in that land. And it was so that when the children of Israel were grown strong they put the Canaanites to taskwork and did not utterly drive them out.'
This summary, like those in Joshua 15:63; Joshua 16:10, summarises the failure of Israel. At first they could not drive out the Canaanites. That was excusable. The Canaanites were too strong and insisted on staying in the land (‘would stay in the land'). But then in each case the opportunity arose and they failed to take advantage of it. Thus when they did for a while obtain control over the cities they took advantage of it to make gains for themselves rather than driving out the Canaanites. Their failure to do so would result in compromise and breach of the covenant through fraternising with the debased Canaanite religion. Compromise and greed are two ever present enemies for the Christian.