Judah and Jerusalem were being punished for the sins of the fathers. Daniel 9:16
16 O Lord, according to all thy righteousness, I beseech thee, let thine anger and thy fury be turned away from thy city Jerusalem, thy holy mountain: because for our sins, and for the iniquities of our fathers, Jerusalem and thy people are become a reproach to all that are about us.
Matthew 23
35 That upon you may come all the righteous blood shed upon the earth, from the blood of righteous Abel unto the blood of Zacharias son of Barachias, whom ye slew between the temple and the altar.
Under the New Covenant, the sons are not punished for the sins of the father, so it stands to reason that the New Covenant only truly came into existence after the punishment of Judah, AD67-73.
27 Behold, the days come, saith the Lord, that I will sow the house of Israel and the house of Judah with the seed of man, and with the seed of beast.
28 And it shall come to pass, that like as I have watched over them, to pluck up, and to break down, and to throw down, and to destroy, and to afflict; so will I watch over them, to build, and to plant, saith the Lord.
29 In those days they shall say no more, The fathers have eaten a sour grape, and the children's teeth are set on edge.
30 But every one shall die for his own iniquity: every man that eateth the sour grape, his teeth shall be set on edge.