When really young prepubescent children were crowned the king/queen of a country how did people react? How did normal people receive children being crowned monarchs, and how did the children handle the responsibility.
Did they ever fuck up diplomatic relations with other nations? Why did armies put up with following orders from small children?
How did they rule if they could barely understand the world around them? Did people take them seriously, did they ever through tantrums and start wars or have people executed?
This is really not so hard a question to answer as you would imagine. The short answer is: they didn't exercise direct power, and for obvious reasons. The slightly longer answer is, prior to achieving something resembling the age of maturity - say, fourteen or fifteen - some permutation on a regency ruled in the young king's stead. The regent could be one person, possibly a mother or other close relative, or it could consist of several individuals, usually powerful lords in their own right.