It's worth recalling just how long it had been since these sacred had been heard. Remember Hezekiah was the last king that observed the law of Moses and active practiced temple worship. His son Manasseh was notoriously evil and he reigned for 55 years in Jerusalem and clearly wanted nothing to do with his father's religion. 2 Chronicles 34:2-9 details the extent of his evil administration. He practised just about everything that God hated (looks like "you name it . . . he did it").
"So Manasseh made Judah and the inhabitants of Jerusalem to err, and to do worse than the heathen, whom the Lord had destroyed before the children of Israel." -- 2 Chron 34:9
After Menasseh, his son Amon rules for 2 years -- equally wicked. So now you have 55 + 2 years = 57 years of darkness. Next comes the righteous Josiah who takes the throne at the tender age of 8 and 18 years later he begins the massive project to cleanse and restore the temple. So 57 years + 18 more years = 75 years of darkness. Let this sink in -- this was a long time! 75 years of no reading of the law, no temple worship, no observance of the holy days. It's a wonder that this culture could produce a Josiah!
It reminds us of the power of the word of God to transform darkness into light and keep evil at bay. As David said,
"Thy word have I hid in mine heart, that I might not sin against thee" --- Psalm 119:11