Democrats actually do really good in rural Wisconsin for the most part, except a few areas like Clark and Taylor counties and that whole area north of Green Bay. It's how they keep the GOP margins down in the other areas and run up the score in Dane and Milwaukee that keeps them competitive in the state.
If rural Wisconsin voted like rural Missouri or rural Indiana they probably wouldn't be able to win much of anything.
There's no county in all of Wisconsin that gave Trump 80% of the vote, and I think only 3 that gave him over 70%. Meanwhile in places like Missouri and Indiana those kind of counties are everywhere.
Dane/Milwaukee is a smaller chunk of the state than KC/St Louis is in MO but MO Dems can't win the state no matter how much they run up the score in KC/St Louis.
If I had to guess, liberal migration into the state boosts the D floor there.