Josiah was eight years old when he became king, He did what was right in the eyes of the Lord

 2 Chronicles 33:21-34:7

Amon was twenty-two years old when he became king, and he reigned in Jerusalem two years. He did evil in the eyes of the Lord, as his father Manasseh had done. Amon worshiped and offered sacrifices to all the idols Manasseh had made. But unlike his father Manasseh, he did not humble himself before the Lord; Amon increased his guilt.

Amon’s officials conspired against him and assassinated him in his palace. Then the people of the land killed all who had plotted against King Amon, and they made Josiah his son king in his place.

Josiah was eight years old when he became king, and he reigned in Jerusalem thirty-one years. He did what was right in the eyes of the Lord and followed the ways of his father David, not turning aside to the right or to the left.

In the towns of Manasseh, Ephraim and Simeon, as far as Naphtali, and in the ruins around them, he tore down the altars and the Asherah poles and crushed the idols to powder and cut to pieces all the incense altars throughout Israel. Then he went back to Jerusalem.

Why?

The evil one is always killed by evil men, like Amon and his officials.

Joasia walked on the right way and followed the ways of his father David. He cut down the idols in Judah and throughout Israel.

Because of these a few good kings the Lord let Judah stand longer than Israel.

How?

Why a man or a king walked in the right way or evil way, depends on his heart. Everyone has to face the Lord one day.