That doesn't talk about the weird lines that Republicans draw on the map. Remember the effed-up lines in PA? I know nothing about Wisconsin districts but I looked up the map and the county that Milwaukee is split into 4 districts with some crazy zig-zag lines. Just a total guess that if the lines were drawn evenly, there would be more Dem house seats. This is what Republicans do. They cheat.
I saw an interview today where it was said that despite Wisconsin being the most purple state in the US, 6 of 8 congressional districts are solidly red. You could say that's because Milwaukee and Madison are the only blue areas and while that's true, most Wisconsinites live in or near those cities. So, I am assuming that lines were drawn to carve up Madison and Milwaukee in a way where Dem neighborhoods were placed into several solidly red districts.