Everything that was happening in Jerusalem was just what Moses predicted. The Israelites had been given the divine formula that could have made them the richest and most powerful nation on earth, but Moses knew that this is not what would happen. At the close of his ministry the Lord told Moses in Deuteronomy 31:27-29 that the Israelites would "utterly corrupt themselves."
Not only had Moses predicted it, but Isaiah had actually seen it in a series of visions portraying the prophetic history of the Israelites for 2,700 years. He was allowed to see the long centuries of apostasy, wickedness, idolatry and debauchery which would not only cause the Lord's chosen people to lose their promised blessings but would even result in their rejecting God's own Son when he came as the Messiah. So the task of Isaiah around 700 B.C. was to tell these people how wicked they really were and what the consequences would be.