In Death of a Salesman, why is Willy ready to commit suicide after his struggle with Biff, whereas before he was not?
After the argument at the restaurant, Willy realized Biff had lied about the job. It was supposed to be a celebratory dinner, because Biff was supposed to have gotten his job back at the sporting goods factory. However, because Willy found out that Biff hadn't been forthright and truthful, it was the last straw; Willy was totally finished trying to help him be successful. Willy himself was no longer successful, and all of the so-called, scatterbrained advice that he had given Biff was no longer of use. The only way he could help anyone, including his wife, financially, was to end his own life and use the insurance money to pay off some bills.
It's very sad that Willy felt he had to go to this extreme. Biff could've been kinder to Willy at the restaurant, but at the same time, Willy had high expectations for him, and since Biff averaged a new job every six months or so, it wasn't exactly realistic for Willy to have such expectations of his wayward son. Willy not only lacked proficiency as a salesman, but also as a father it would appear.