Mike Mahan, left, who leads Fanatics’ collectibles division, speaks to business owners at the Chicago Sports Spectacular at the Convention Center in Rosemont, Ill., on Nov. 18, 2023. Powered by its connections with leagues and star athletes, Fanatics, the merchandising giant has entered the hobby universe with deep pockets and sharp elbows. Not everyone is happy. (Jamie Kelter Davis/The New York Times).