How do motifs further our understanding of the themes within The Grapes of Wrath?

A “motif” in a work of literature is a subject, theme, or general idea that is repeated many times. (Note: a motif is similar to a theme but with an important difference: a theme is a central idea; motifs serve to further develop and enhance themes through repetition.)
Here are the dominant motifs in John Steinbeck’s The Grapes of Wrath:
The Tyranny of Industrialized Agriculture:
The tractors have come to plow under the homes of the squatters. These farmers have no legal right to the land. When the tractor driver tries to explain that he has a family to feed, and that he is just doing his job, the tenant argues:
But for your three dollars a day fifteen or twenty families can't eat at all. Nearly a hundred people have to go out and wander on the roads for your three dollars a day. Is that right?
Industrialization strips humanity from farming and farmers:
Some of them hated the mathematics that drove them, and some were afraid, and some worshiped the mathematics because it provided a refuge from thought and from feeling. If a bank or a finance company owned the land, the owner man said, The Bank - or the Company - needs - wants - insists - must have - as though the Bank or the Company were a monster, with thought and feeling, which had ensnared them. These last would take no responsibility for the banks or the companies because they were men and slaves, while the banks were machines and masters all at the same time.
The senselessness of valuing profit over people:
The works of the roots of the vines, of the trees, must be destroyed to keep up the price, and this is the saddest, bitterest thing of all. Carloads of oranges dumped on the ground. The people came for miles to take the fruit, but this could not be. How would they buy oranges at twenty cents a dozen if they could drive out and pick them up? And men with hoses squirt kerosene on the oranges, and they are angry at the crime, angry at the people who have come to take the fruit.
The Faceless Enemy:
"No, you’re wrong there—quite wrong there. The bank is something else than men. It happens that every man in a bank hates what the bank does, and yet the bank does it. The bank is something more than men, I tell you. It’s the monster. Men made it, but they can’t control it."
Violations of Civil and Human Rights:
There is a crime here that goes beyond denunciation. There is a sorrow here that weeping cannot symbolize. There is a failure here that topples all our success. The fertile earth, the straight tree rows, the sturdy trunks, and the ripe fruit. And children dying of pellagra must die because a profit cannot be taken from an orange.
Resilience of the People:
“Women can change better’n a man,” Ma said soothingly. “Woman got all her life in her arms. Man got it all in his head.”
“Man, he lives in jerks-baby born an’ a man dies, an’ that’s a jerk-gets a farm and looses his farm, an’ that’s a jerk. Woman, its all one flow, like a stream, little eddies, little waterfalls, but the river, it goes right on. Woman looks at it like that. We ain’t gonna die out. People is goin’ on-changin’ a little, maybe, but goin’ right on.