MN was settled by Swedish,Norwegion, Germans and others. The first three are mainly all of the Lutheran faith which is very liberal and thus families for generations have voted for Democrats because their great grandfather did.
That may be true in MN, but the Germans that came here to Pittsburgh were often Catholic or Protestant but not Lutheran(or at least my ancestors).
Actually, MN did not turn permanently Democrat until 1948, when HHH won them over.