Stadium extortion is another issue.
Towns, including those that really aren't "major" cities want to be thought of as such, and having a pro sports team is a way to get in that particular d*** measuring contest.
Cities which have been misgoverned into decay want to pretend that it is some, contradictory, combination of not really true and going to get better soon. New shiny stadiums, combined with what will usually be called "a mixed use development" (i.e. a mall for rich people, some over-priced apartments, and a dog park) are often a part of the latest "revitalization plan" for a blighted downtown.
In both cases, the local pols tax people that really have no interest in the matter, including in some states, people that live very far away from the cities in question.