What does Esther mean when she says these things are not Beah's fault? Does he believe her right away? Why? Or why not?

Esther tries to convince Beah that his family dying and his war-time experiences were not his fault. Beah was a victim of circumstances that were beyond his control. I think that at this point, Beah is still confused and frustrated. Slowly Beah opens up to Esther and he is able to put his experiences in some kind of context.