“What sorrow for those” is a statement made by Isaiah multiple times and in each instance he was specifically describing various actions that GOD considered to be evil and the coming judgment as a result.

However, His frustration wasn’t only with the people of Judah. He also was angry with the Assyrians and their king. For even though the Assyrians were GOD’S tool to punish the Israelites, the Assyrians needed to be dealt with as well.

And how GOD ultimately deals with the sin of all nations, is through the Messiah, the root of Jesse.