I thought one of the major reasons for the collapse was that the invaders learned how to make weapons of iron, which took away the weapons advantage of the Civilized bronze weapon people? Much of this covered in the excellent book "1177 BC: The Year Civilization Collapsed". The book adds that the Israelites may have been invaders that displaced more civilized Canaanites around this time (coincident with some of the Biblical stories, like the fall of Jericho?)