The fact that a child (and to some extent also an adult) dreams of grandeur is, in fact, a general phenomena.
Many children dream, in some stage or another of their life, to become kings, governors, conquerors of the world and its rulers.
And without doubt the dream about becoming messiah has resemblance to all these dreams.
Being part of the thinking capacity of the child, they are magnificent and grand dreams without considering the practicality and possibility of achieving them.
–Rabbi Adin Steinsaltz