In the first part of My Antonia, why do so many immigrants risk their lives to leave their homelands and attempt to start over on a harsh prairie with little or no money?

My Antonia showcases the lives of two different families—the Burdens and the Shimerdas—as they navigate their lives on a Nebraska plain in the late nineteenth century. The Burdens have lived there for many decades; the Shimerdas, on the other hand, immigrate from Bohemia, a move that proves to have many trials and tribulations. In short, the reason the Shimerdas even attempt to immigrate—despite having no money and no real sense of American life or culture—is because they genuinely believe their opportunity is still much greater in America than in Bohemia, or really anywhere else, for that matter.
It is worth noting that Mr. Shimerda ends up committing suicide within the novel, which showcases the genuine emotional struggles that can come with immigrating from another country. Mr. Shimerda was content with his life in Bohemia, but his wife thought they would be better off—economically, financially, emotionally, and spiritually—in the United States. So, even having little money and very little idea of the culture, they took the risk. This risk isn't unlike the risk that many immigrants took at the time—America has always served as an alluring option for religious freedom and opportunity, as well as opportunity for unlimited potential of wealth. While this certainly isn't the case for everyone, the idea of possibility is sometimes enough to convince people to leave their countries behind in hope of something better.