"While Manasseh may have been an ungodly king in the beginning, he redeemed himself somewhat in the end. Manasseh reigned longer (55 years) than any other king and had the dubious distinction of being Judah's most wicked king. He came to the throne at the age of 12.  He reverted to the ways of his evil grandfather, Ahaz.

Committed to idolatry, Manasseh restored everything Hezekiah had abolished. Manasseh erected altars to Baal; he erected an image of Asherah in the Temple; he worshiped the sun, moon, and stars; he recognized the Ammonite god Molech and sacrificed his son to him, he approved divination; and he killed all who protested his evil actions.

Manasseh was temporarily deported to Babylon where he humbled himself before God in repentance. Upon Manasseh's return to Jerusalem, he tried to reverse the trends he had set; but his reforms were quickly reversed after his death by his wicked son Amon."
(from Nelson's Illustrated Bible Dictionary, Copyright (C) 1986, Thomas Nelson Publishers)

Contrast the above description of Manasseh to his grandson Josiah.

II Kings 23:25
Neither before nor after Josiah was there a king like him who turned to the LORD as he did-- with all his heart and with all his soul and with all his strength, in accordance with all the Law of Moses.

What a statement to Josiah’s character! Notice all the “all”s.

We have reference to this commandment in the gospels. Jesus clarified and gave details of the original commandment given to Moses.

Mark 12:30
and you shall love the Lord your God with all your heart, and with all your soul, and with all your mind, and with all your strength."  This is the first commandment.

However, even a godly person like Josiah can still suffer because of the sins of others.

II Kings 23:26
Nevertheless, the LORD did not turn away from the heat of his fierce anger, which burned against Judah because of all that Manasseh had done to provoke him to anger.

When Manasseh repented of the evils he had done, he restored the altar of the Lord in the temple and began proper sacrificing again.  However, the people continued to offer sacrifices to God on the pagan high places.  Even though they were worshiping God, they were worshiping in vain because the worship was done in pagan ways.

Josiah did what was right, however the people did not. Sin has consequences. Innocent people can suffer because of the sins of others. Sin is as an open wound. The wound may heal but often scars remain.