John Gill Commentary 2 Kings 16:12

"And when the king was come from Damascus, the king saw the altar: and the king drew near unto the altar, and offered thereon." — 2 Kings 16:12 (ASV)

And when the king was come from Damascus, the king saw the
altar
Looked at it, and liked it, being exactly according to the pattern he had sent:

and the king approached the altar, and offered thereon ;
either by a priest, or it may be in his own person, having no regard to the laws and appointments of God, and especially as his sacrifices were not offered to him, but to the gods of Damascus and Syria, (2 Chronicles 28:23) .