For a king of such great power like David, ruling the Kingdom of Israel was an enormous task. He constantly faced ruthless enemies, whom even he could not defeat by himself, but time and time again had to call upon God for the victory.
It makes you wonder what God had in mind when He allowed 8-year-old Josiah to rule over the whole Kingdom. Surely so many people wagged their heads in unbelief toward the child, doubting his ability to rule such a great nation. However, Josiah had something going for him the preceding King did not.