Would you prefer to be ruled by a 12 yr old or an 8yr old?The myopic focus on the fascinations of a preteesn, Manassah, had dire consequences on a kingdom and peoples, even sacrificing his own son in a fire!
When Joash became king he was eight years old, a time when in usual childhood development he would be learning that the world did not necessarily revolve around him! He would have been more inclined to listen and consider.
What influences had the two available to them?
The mothers of both were mentioned in the text. Joash also has priests in his life, and knows who is trustworthy in the temple. There appears to be a calmness in Joash's reign that would help in doing repair work to the temple. Indeed, it was 18yrs into his reign that his activities are mentioned. Through his work the book of the Law is found, and again the character of the man is seen when confronted with the shortcommings of the nation.
19 "Because your heart was responsive and you humbled yourself before the LORD when you heard what I have spoken against this place and its people—that they would become a curse and be laid waste—and because you tore your robes and wept in my presence, I also have heard you, declares the LORD. 20 Therefore I will gather you to your ancestors, and you will be buried in peace. Your eyes will not see all the disaster I am going to bring on this place.' "
Not so with Manassah, there is a frenetic activity communicated through the text. building altars, making sacrifices, spilling innocent blood etc.
16 "Moreover, Manasseh also shed so much innocent blood that he filled Jerusalem from end to end—besides the sin that he had caused Judah to commit, so that they did evil in the eyes of the LORD. As for the other events of Manasseh's reign, and all he did, including the sin he committed, are they not written in the book of the annals of the kings of Judah? Manasseh rested with his ancestors and was buried in his palace garden, the garden of Uzza".
What was the end of both men,
Manasseh rested with his ancestors and was buried in his palace garden, the garden of Uzza"
2 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.
Manasseh may rest with his ancestors, but Josiah will rest in the heart of God.
Josiah fulfilled the prime directive:"Love the Lord your God with all your heart soul, mind and strength"