Answer:
Boo Radley' motivation is his privacy and his feeling of being independent, and some would say to look after his "children". As we know Boo Radley stays inside for most of the story until then where he rescues Scout and Jem from certain death. He likes to stay inside because he does not want to go outside. Towards the end of the book, Scout Finch walks Boo Radley down to his place and when she walks back to her house; she sees things from Boo Radley's point of view and sees how Boo thinks of them as his children. So from this, we know that Boo Radley has been watching Scout and Jem frequently; and that he saw them as his children and this would motivate Boo Radley to keep his children(Scout and Jem) safe from any harm. So although Boo Radley only appears at the end scene his motivation has been there throughout the whole story.
Step-by-step explanation: