How does Tom’s new philosophy/theology—which he learned from Casy—reflect Steinbeck’s Socialist views?

Certainly taking care of each other rather than the classic American spirit of independence is at play here. Picking oneself up by the bootstraps so to speak doesn't work when a person has no boots. Steinbeck felt the type of capitalism involved with starving thousands of families was not acceptable. He felt there must be a minimum of a welfare-state to preserve a shred of human dignity.