The Question and Answer section for The Grapes of Wrath is a great resource to ask questions, find answers, and discuss the novel.
The preacher lost the spirit because he turned his back on the message he was preaching and indulged in the things he preached against. His guilt and shame left him unfit for his calling. Thus, he walked away.
This is a pretty detailed question for this short answer forum. There are a few scenes you might consider. As the sun rises on Casy, the former preacher and Christ-figure, has a glow about him which illustrates a sense of grace. Tom appears in he...
Ma said she feared they would stop the car if the knew Grandma was dead and they would never get across the desert.