As someone who was born in Wisconsin, and lived there for the majority of my life, I have to say that the NBA is not especially popular in the state. Even non-cheeseheads, sports enthusiasts or otherwise, would tend to think of the Green Bay Packers upon hearing the word "Wisconsin". People just don't talk about the NBA in general, or the Milwaukee Bucks in particular, all that often. The city of Milwaukee may be an exception, but the city is also quite unlike the rest of the state.
The NBA may not be as popular as other sports in Wisconsin, but there is a long tradition of supporting basketball, lacrosse, hockey, and other winter sports in this cold, winters state. Not everyone is a fan of football, and many people are fans of both football and basketball in Wisconson.
No, the NBA is not popular in Wisconsin. While many people in Wisconsin like basketball, and while it may be that there are several basketball teams based in Wisconsin, the sport does not enjoy much popularity there compared to other states. Football, especially considering the love shown to the Green Bay Packers, is much more popular.
Wisconsin is a cold place. There are other things in Wisconsin that are more popular than the NBA. The Green Bay Packers are an example. They are one of the most popular sports teams in the NFL. Hockey is also very popular in Wisconsin because there is great weather in the winter for hockey.