Charles Spurgeon Commentary 2 Chronicles 28:1-3

"Ahaz was twenty years old when he began to reign; and he reigned sixteen years in Jerusalem: and he did not that which was right in the eyes of Jehovah, like David his father; but he walked in the ways of the kings of Israel, and made also molten images for the Baalim. Moreover he burnt incense in the valley of the son of Hinnom, and burnt his children in the fire, according to the abominations of the nations whom Jehovah cast out before the children of Israel." — 2 Chronicles 28:1-3 (ASV)

Ahaz was twenty years old when he began to reign, and he reigned sixteen years in Jerusalem: but he did not that which was right in the sight of the LORD, like David his father: for he walked in the ways of the kings of Israel, and made also molten images for Baalim. Moreover, he burned incense in the Valley of the Son of Hinnom, and burned his children in the fire, after the abominations of the heathen whom the LORD had cast out before the children of Israel.

God had driven out the Canaanites because of these abominations; therefore, for His own people to practice them, was especially provoking to Him.