The closing scene in the novel's final pages of the family wandering the streets of San Francisco making a noble effort to convert people to Christianity might be seen as the resolution that Clyde seems unable to provide during his time in prison before his execution. Depending on your religious view and on your opinion on the novel's religious message, this final scene in San Francisco can be seen as more Naturalist weakness and futility OR a beam of bright Christian hope at the end of a long, dark meditation on the nature of human weakness and inherent sinfulness.
The novel is influenced by the philosophy and literary movement called “Realism and Naturalism,” which means that it tries to depict life in an unsentimental way. It shows characters developing as a result of their circumstances in life so that those who are strong succeed, and those who are not fail or are trampled upon by the strong. “Strength” proceeds from stability in wealth, social position, family ties, and so on. The resolution of the novel is consistent with this. Clyde acquires wealth not by working for it but by circumstance, not understanding responsibility and hard work. Although he did not in fact murder Roberta, he intended to, and he is eventually electrocuted for a crime he wanted to but did not commit. He dies as he lived, not taking responsibility for his life or death. His background, poor, destined him for such a miserable end.