I think humans have a default toward tribal thinking. We view "us" as superior and more cherished than "them". I don't think most people will agree that they, personally, are prone to it; but it shows up in a hundred different way in life. I spotted that thinking in myself when I saw that the next oracle wasn't a terrible foreign enemy, but our Jerusalem. This should remind us that when we act like the enemies of God, we shouldn't be surprised to find ourselves on a list that includes those we're acting like.
It seems like this chapter is related to the events immediately before, during, and/or after the reign of Hezekiah.
According to the NASB Ryrie Study Bible organization, Chapters 3 and 4 combine in a sub section titled, A Message of Doom and Deliverance. There was much doom in Chapter Three. Bring on the deliverance!
Isaiah begins with his indictment of Judah's behavior and a prophesy of their future which is also a parallel to the end times. Then we flash back to read about his calling. Now we are back in his historical timeline with the kings of his time.
Chapter 3 ends with the proud, seductive daughters of Zions being taken and abused as slaves in this time of terror and desolation. Chapter 4 opens with women so desperate for a husband, they agree to support themselves.
So we finally have the house of Ahab scrubbed from Israel and Judah. Jehu meeting God's mandate and then far exceeding it in brutality to secure his authority on the throne in the north; and the Lord using the high priest and his wife to save the remaining offspring in the line of David, taking the throne at the tender age of 7.
Kings Jehoshaphat and Ahab are both dead. We've finished I Kings and now II Kings and II Chronicles spreads out over the chronological timeline. The Blue Letter Bible (BLB) chronological reading plan lists Obadiah now, prior to beginning II Kings. Although this is disputed.