In "The Harvest Gypsies: Article II," what effect does Steinbeck's straightforward expository style have on the level of empathy readers feel for the people he describes?

In "The Harvest Gypsies: Article II," Steinbeck zooms in on three families living in a migrant worker camp. In the first article, he provided facts and figures about the number of migrant workers driven by Dust Bowl drought to central California. This created a logical framework that oriented the reader to what was going on. In this article, however, he moves from fact to personal stories.
Stories have an emotional impact because they are up close and personal. Emotion builds empathy in a way that facts can't because we can relate to stories.
Steinbeck tells us about these three families in a flat, deadpan, journalistic style, which seems, at first glance, to work against building empathy. Contrary to what one might expect, however, Steinbeck's style of writing is especially effective for raising emotion and creating empathy. This is because Steinbeck does not tell us what to feel, nor does he feel our emotions for us by expressing outrage and saying how horrible it all is. The emotional impact is all the stronger because Steinbeck simply shows us what is going on: he gives us the facts and then backs out of the way. From the details he provides, we can draw our own conclusions, feel our own feelings, and decide for ourselves that the situation is terrible.
Steinbeck follows several rules of thumb for building empathy: first, he offers details that build an image in the reader's mind. Further, he focuses on specific families, which builds empathy with them, and he emphasizes the dignity and innocence of these people. He provides background about these families that show they were once middle- or working-class people and are destitute through no fault of their own. For example, he tells of us the second family:

The father of this family once had a little grocery store and his family lived in back of it so that even the children could wait on the counter. When the drought set in there was no trade for the store any more.

Because we can visualize how these people lived and because they did not deserve poverty, they are relatable. We can picture working hard ourselves to own a store and then losing it to an environmental disaster that leads to economic collapse. These simple, unembroidered facts build our empathy.
In the camp we can empathize too. For example, we can relate to the attempts of the first family to keep clean because Steinbeck shows us in stark language their attempts to do so:

The dirt floor is swept clean, and along the irrigation ditch or in the muddy river the wife of the family scrubs clothes without soap....

Because we know that how hard they are trying, we feel all the worse when Steinbeck tells us that

With the first rain the carefully built house will slop down into a brown, pulpy mush.

The words "brown, pulpy mush," straightforward and unemotional, build a picture in our minds which makes us feel how awful this will be for this family. Such descriptive details evoke emotion.
Steinbeck also depicts young children suffering, which has an especially strong emotional impact, because we know the children are innocent victims. We are hardwired to want to protect children.
For example, in the case of the second family, we learn of the four-year-old:

One night he went into convulsions and died, and the next morning the coroner’s wagon took him away.

By stating it so plainly, Steinbeck leaves us room to feel emotional pain.
In the case of the third, most desperate family, we learn that the hungry, listless three-year-old with the distended belly quite simply

will die in a very short time.

Steinbeck's expository prose doesn't sugarcoat what will happen, and so we feel the impact.
In sum, a straightforward, stark, "just the facts" style get the writer out of the way and allows the reader to build a relationship with the people described. We can picture their situation and feel how they must be feeling.