I think a lot was finding a better life in America. People "back home" had letters from family who had already immigrated. In my own family, one would come over, find work and save enough to pay the passage of the second one. Then those two would bring over a third, and so on till the whole family was over. In the late 1800's-early1900's America was young and needed laborers for the factories, breweries, etc. My own relatives, tho not wealthy, were able to make a decent living, better than they had back in the homeland.