John Gill Commentary 2 Kings 8:27

"And he walked in the way of the house of Ahab, and did that which was evil in the sight of Jehovah, as did the house of Ahab; for he was the son-in-law of the house of Ahab." — 2 Kings 8:27 (ASV)

And he walked in the way of the house of Ahab, and did evil in
the sight of the Lord, as [did] the house of Ahab
Worshipping the calves, and Baal also:

for he was the son in law of the house of Ahab ;
he was the son of Jehoram, who was son-in-law to Ahab, having married his daughter, which accounts for his being guilty of the same idolatrous practices.