NOTES for Jdg 2:1-23
As one can see, what Joshua feared is exactly what happened to the people: the generation of those who conquered the land passed away, and with its passing religious enthusiasm gave way to decline. There is nothing surprising here: religious enthusiasm cannot last forever, and it cannot be any reliable foundation for spiritual life, or for life in general. The younger generation, which knew about the war only from their fathers' stories, did not see in paganism and in pagan gods anything incompatible with Yahwism.
The conquerors of the land could not even imagine the possibility of worshiping any gods other than Yahweh, or the appearance of altars to these gods on their land. Even ordinary monuments were under suspicion: zealots of orthodoxy asked whether they would become objects of religious worship, whether a new, alternative religious center would arise around such a monument. The young people looked at the matter more simply. Representatives of the younger generation were not such rigorists as their fathers, but at the same time the very understanding of Yahwism, of the limits of what was possible and permissible, was being blurred.
This blurring was greatly helped by the outlook of people who had only recently been introduced to settled life, and therefore to settled civilization. They often looked at the religion of the local inhabitants as the religion of civilized people, and at Yahwism as the faith of half-wild nomads (forgetting, of course, that it was precisely the religion of those "wild nomads" that had allowed them themselves to settle in the land where they lived and to join the civilization they so desired). Formally, of course, no one renounced Yahwism, since it was the faith of their fathers, but in practice they began everywhere, alongside Yahweh, to worship local gods, especially the baals who patronized specific territories, and the Great Goddess, venerated throughout the ancient Near East and known in Palestine by the name Asherah (the "Astarte" of the Synodal translation).
Asherah began to be perceived as the "divine spouse" of Yahweh Himself, and the local baals as His children or subjects. This was no longer monotheism, but something like the Olympian religion with its pantheon, and most Hebrews found this version entirely acceptable. The exception was the judges, charismatic leaders connected with the prophetic movement, whose representatives always remained champions of strict monotheism.
But they were remembered when the situation became critical, usually because of military conflicts with pagan neighbors who remained in Palestine. It is not surprising that God refuses to drive out the pagan population: if His own people not only have nothing against it, but have even essentially become pagan themselves, why shield them from what they are drawn to and long for? Thus the worst expectations of Joshua were fulfilled, for he understood the fragility of religious emotions and the religious upsurges connected with them.