Simple answer was that they were looking for jobs.
The Arnlod-Franchis came from Altdorf in the German speaking part of Switzerland, where Josef was a farmer. Altdorf is very close to the canton of Glarus in Switzerland, where there was a lot of povery in the middle and late 19th Century. This resulted in the formation of Glarus Emigration Society, the principal aim being for the young people to move and get established in America. The pioneers sent by that society explored prospects in several states of the Midwest before establisng a settlement in southern Wisconsin, where New Glarus is now present.
The 1971 Swedish film The Emigrants starring Max von Sydow and Liv Ulmann has a similar background theme but its about the lives of Swedish immigrants in Minnesota. The Criterion Blu-ray is a superb package.