John Gill Commentary 1 Kings 16:19

"for his sins which he sinned in doing that which was evil in the sight of Jehovah, in walking in the way of Jeroboam, and in his sin which he did, to make Israel to sin." — 1 Kings 16:19 (ASV)

For his sins which he sinned in doing evil in the sight of the
Lord
In the former part of his life, as well as now:

in walking in the way of Jeroboam, and in his sin which he did to make
Israel sin ;
worshipping the golden calves, which he might do while a captain of the chariots, and also since he usurped the crown, sacrificing to them by way of thanksgiving, for being in possession of the kingdom; and though his reign was so short, he might give plain and strong intimations that he should continue the worship of idols.