Isaiah delivers a formal prophecy couched in formal referential terms. There are two parallel phrasings defining each of the conspiring kings. They are referred to in their positions of leadership of a people, beginning with their capital city, and then with the individual as the leader of the city. The effect of the formal delineation of the right of rulership for these two kings is to place the prophecy in an official context. Isaiah is saying that it is true that the “head of Syria is Damascus, and the head of Damascus is Rezin.” That is a known and undisputed truth. Just as that is true, and just as the similar concept for Remaliah’s son is true - so is the prophecy couched between these two patently true statements.
The message, however, is not in the truth of the statements of the kings, but the particular prophecy. Within 65 years the house of Ephraim will be destroyed. Ephraim will no longer be a “people,” or an independent nation.
Ahaz is given this information, and is shown the weight of it. He is told to believe, or else Ahaz will “not be established.” His own kingdom depends on his heed to this prophetic assurance. Isaiah does not tell us why there is a correlation between Ahaz believing this prophecy and his own survival as king. We can read into this statement the contexts of history, and understand the reason. Ahaz had determined that he required a powerful alliance of his own, and made such an alliance with Assyria. In some way, Ahaz’s political alliance with Assyria provided the invitation for military action by Assyria that would create tremendous destruction not only in Israel, but also would result in subjugation of Judah.