I would love to agree with you here, but there are way too many Packer fans in the Chicagoland area. I am always amazed by the volume of Cubs fans who are also Packer fans. It is quite annoying to me.
In modern times, there has always been a rather tight relationship between Northern Illinois and Wisconsin.
Many Chicago area families take frequent vacations in the various Wisconsin resort areas. And they make friends there or have family there.
Wisconsin people come down to Chicago to visit family members, to spend some time in a World Class city, and to watch the Brewers, Bucks, and Packers. Milwaukee was even flirting with the idea of getting an NFL franchise years ago but they found the franchise fee to be paid to existing NHL owners not within their budget.
There are colleges and universities in both the Chicago and Wisconsin areas (Milwaukee, Madison, and others) that bring tens of thousands of Illinois and Wisconsin young people together. Many Illinois-area college grads took jobs up North and may have got hooked up to the Green and Gold over the years.
Now, none of this by itself will answer for why there are so many Packer fans in Chicagoland. But the fact that the Bears and Packers are two long-standing legacy NFL franchises with an unmatched rivalry means that there is a lot of cross-pollinating going on for a very long time.
And some at-one-time-Bear fans that are on the North Side of Chicago and near the State line have switched loyalties from a troubled Bears franchise that hasn’t been good since in the 1940s.. to a nearby regional team that has seen some great success in the decades since then. Not to mention the mystique about the legendary coach and Hall-of-Fame players the Pack have had since the 1960s.
Because the Wisconsin franchise has had so much more success than the Bears in the last 60 years... it’s understandable why more Chicago people maybe took on a Packer interest than a Wisconsin person ever adopting The Bears. People just like getting attached to a winner.
But I get what you’re saying. Many White Sox fans find it annoying that there are so many Cub fans on the South Side areas of Chicagoland.
There are probably as many reasons why a person has adopted a loyalty to some team as there are sports fans. But rivalries really make sports hot and spicy.