During Scene 9, Willy desperately sorts through memories of Biff's childhood in order to explain to himself why Biff failed with Oliver. He cannot understand why Biff let his last opportunity for success pass him by. It is only when Biff reveals his reason for going to see Oliver that Willy finally understands: "Why did I go? Why did I go? Look at you! Look at what's become of you!" Biff went to see Oliver to please his father and to prevent Willy from suffering a complete mental breakdown. Biff fails with Oliver, just as he did in high school, and Willy is to blame for failures of both the past and present. Even though Biff still wants to satisfy Willy, he cannot because his esteem for his father has been irreparably damaged by knowledge of the affair.
During Scene 10, once Biff discovers that his father is not perfect, and even worse, that he is a traitor to his mother, Biff loses all respect for Willy. He realizes that everything Willy said to him means nothing. The affair negates all of Willy's tales of greatness that have motivated Biff up to this point. Why should he attend summer school or hold a steady job? Need for his father's approval no longer guides his actions. As a result, Willy is responsible for Biff's downward spiral. Biff did not attend summer school or graduate because of Willy's perfidy. Now he is incapable of achieving success because he possesses no faith in his father or himself.
