Why is Bruno curious, adventuous and friendly in The Boy in the Striped Pajamas?

It seems to me that in order for the story "to work,"
Bruno has to be shown in the purest form of a child.  Bruno's childhood innocence and
perception of the world is what allows the story to acquire its greatest significance. 
Accordingly, Bruno has to represent those qualities within childhood such as curious,
adventurous and friendly.  In representing these qualities, Bruno's character
demonstrates a timeless and transcendental vision of childhood.  In the most bleak
setting, where childhood is eviscerated on an alarmingly high basis, Bruno's character
helps to bring light to the fact that the positive of qualities of hope and redemption,
particularly of childhood, have to be seen as stronger as the forces of negation, as
seen in the Holocaust.  If Bruno is seen in any other way, these negation forces seem to
prevail.  The development of Bruno's character, replete with a sense of curiousness as
well as one willing to undertake quests that represent only hope and nothing else, is
what allows to make his friendship with Shmuel so beautiful and tender, one that sees
them embracing their friendship even until the last moments of their
life.