Josiah became king of Judah while he was still very young. He was 8 years old. After he had grown into adulthood, he took the time to evaluate both the fiscal condition of the temple as well as the state of the facilities themselves. He found sufficient funds to do some necessary repairs, so, the revitalization of the temple began.
As this project commenced, the high priest "found" the Pentateuch. That is, he found the writings of Moses... the Bible, as it was in his day. He found it!? He FOUND a Bible. I presume that means that he hadn't read it previously?! Yet, he was the high priest! How could he be high priest without possessing, examining and using a Bible? It's virtually incomprehensible. But it was true. Hilkiah the high priest, Shaphan the scribe and Josiah the king were the 3 men who should have been the most thoroughly familiar with God's written Word, and yet they had apparently never even seen it, much less read or obeyed it knowingly.
Well, regardless of how they got where they were... God started to work with them from there. When the scribe read the Bible to King Josiah, he went almost berserk - not in anger, but in holy fear. He immediately sent to Huldah the prophetess to find out what message the Lord had for him. Her message was mixed with good news and bad. The terrible threats which Moses had written from the Lord were not hollow bellows. Judgment WAS coming. That was the tough news. But, because of Josiah's tender heart and humble spirit, God promised to wait until after Josiah’s death to wreak havoc in Judah.