“In the twenty-third year of King Joash son of Ahaziah, of Judah, King Jehoahaz son of King Jehu began to reign over Israel in Samaria. He reigned seventeen years. He did what was evil in the sight of Yahweh. He followed the sins of Jeroboam son of Nebat, by which he caused Israel to sin. He did not depart from them.”
Since King Joash in Judah ruled for 40 years, there will be a lot of changes in Israel. Notice that the kings in Israel almost have the same names. Just like the problem with the names Jehoram and Ahaziah. You can go back to chapter 10 to learn about King Jehu his father. King Jehoahaz ruled for 17 years, not that long, near the end of the reign of King Joash in Judah, so that they both die in the early 8th century BCE. We are now about 100 years removed from Solomon so that the split between Judah and Israel seems permanent. King Jehoahaz followed the evil ways of the Israelite founder King Jeroboam.