When Claude learns about Mr. Weisfeld's life before he came to the United States, why does Claude feel guilty and irritated with himself?

When Claude learns about Mr. Weisfeld's life before he came to the United States, Claude feels guilty and irritated with himself because he did not ask to hear about Mr. Weisfeld's life sooner. Claude's depression intensifies because he is angry with himself for not learning about Mr. Weisfeld's life until the day before Mr. Weisfeld died.