John Steinbeck's novel The Grapes of Wrath is full of many good and moral characters as well as many evil and corrupt ones; deciding which he prefers is a matter of examination and your own judgment.
While some characters who act immorally are rich (at least compared to the poverty-stricken Okies), not all of the people with money are morally bankrupt. Compare the greedy, conniving owner of the car dealership, for example, with the cook and waitress at the diner in chapter fifteen. When the man and his boy come in to buy what bread they can, the two diner employees and the truck driver (who are all considered rich in this story because they have steady jobs) all act morally and give the man more bread than his money will buy plus a treat for the boy. So, money is not the only standard for corrupt, evil behavior (though greed for more money certainly causes people to do evil things).
Not having money is also not an indicator of moral and immoral behavior. Plenty of poor people are kind and willing to share what little they have with others in need, such as when Ma Joad lets the children have the leftovers in the cooking pot; others "steal" from the poorest by being willing to work for less than it costs to live.
If he'll take twenty-five, I'll do it for twenty.
Not me, I'm hungry. I'll work for fifteen. I'll work for food.
Religion has little to do with good and bad behavior in this novel, either. While Jim Casy gives his life selflessly for others because he understands that everyone is connect in "one soul," others who claim to be religious have nothing and share nothing but negativity, as Lisbeth Sandry does in chapter twenty-two when she scares the pregnant Rose of Sharon.
You get the point that Steinbeck is not condemning or elevating people based on their circumstances but on their choices. In fact, some of the people who are most moral in this novel have actually done many immoral things. Jim Casey was a rather worldly preacher and used his position to have sex with girls; he now makes different choices and is responsible for the beginning of labor unions which will guarantee better conditions and pay for the workers. Tom Joad was in prison for murder--and commits murder again--but dedicates his life to ensuring a better future for poor workers.
Some characters are consistently evil, like the "enforcers" at the camps and farms, the police, and others who are more interested in keeping the workers out than doing their jobs. Some characters are consistently good and moral, as Ma Joad and Sairy Wilson.
Perhaps the most consistent difference in this novel between the "good" people and the "bad" people is whether or not they own something. Those who own things want to keep them at all costs, and it is their fear of losing them which prompts them to be cruel.
The local people whipped themselves into a mold of cruelty. Then they formed units, squads, and armed them--armed them with clubs, with gas, with guns. We own the country. We can't let these Okies get out of hand. And the men who were armed did not own the land, but they thought they did. And the clerks who drilled at night owned nothing, and the little storekeepers possessed only a drawerful of debts. But even a debt is something, even a job is something.
It is still the choices people make which determine their morality; in the end, though, I suspect Steinbeck thought most people are essentially good, because he ends the novel with Rose of Sharon's selfless act.