Why does doodle brother leave him in the storm?

Doodle's brother leaves him in the storm out of frustration and a desire for freedom. Overwhelmed by the pressure of caring for Doodle, who has physical limitations, he abandons him in a moment of anger. This decision ultimately leads to a tragic outcome, highlighting the themes of guilt and responsibility in their relationship. The storm serves as a metaphor for the turmoil in their bond and the consequences of his actions.