When they came "here" they adopted German?
Where is here?
If it's USA - why German?
The things Americans don't know about their own country would fill a basin as big as the Pacific.
In the mid-1600s you had your Dutch in New York speaking 35 different dialects, and the French everywhere North of the Ohio. The Spanish were just West of the Appalachians, and there were Indian tribes all over the place.
Then there were the English ~ a pitiful people barely able to eke out a living, and reduced to raising such Indian crops as tobacco and marijuana.
Newcomers missed all that.