I'm speaking as a former Cardinals football (minor) fan (the Cardinals left STLMO in search of yet more money...but we won tons of money in suing them and winning).

Although the city and state will be taking a hit on income taxes collected from visiting and home players and staff since they no longer work in the city.

Several reasons. Everyone that lives where taxpayers are funding the stadium pays into it whether they use the stadium or not. It mostly is for millionaire athletes who most live outside of the city limits so you don't see much of a multiplier effect as you see with other things. There are other things you can spend the money on that will help your city in a lot of cases more than a sports stadium. Also most of the businesses that rely on the sports stadium do so mostly during the season.

You're right though that athletes pay multiple state income taxes though but for the money that it costs to build stadium there are other things that would have a better return on investment.

But traffic on game day in that area is going to be awful. Soldier Field is well served by public transit.

Not in or from Chicago, but have family there. Isn't it generally considered that most of the Chicago wealth is north of downtown? Monied season ticket holders and corporate skyboxers are going to schlep down to to NW Indiana on game day? I realize its all part of same MSA and commuting long distances is already part of the mega metropolis ethos...but this feels...out there. Especially with a franchise so storied and tied to the City of Chicago.

They could pay for their own stadiums but they don't need to because of the leverage they have.