John Gill Commentary 2 Kings 15:3

"And he did that which was right in the eyes of Jehovah, according to all that his father Amaziah had done." — 2 Kings 15:3 (ASV)

And he did that which was right in the sight of the Lord
At the beginning of his reign, and in an external way:

according to all that his father Amaziah had done ;
who did not do what he did as David, sincerely and cordially, (2 Kings 14:3) (2 Chronicles 25:2) .