Read about the dissimilarity in terms of statistics of Chicago Cubs v/s Chicago White Sox fans.
The Cubs are located on the North Side of Chicago and the White Sox on the South Side. This impacts demographics. A White Sox fan is more likely to be blue-collar. That said, the blue-collar part is much more dominant. The typical White Sox fan is a blue-collar person from a western or southwestern suburb.
The main reason for that is that the Cubs withdraw from a much bigger geographic area. Most of Illinois is Cubs territory, and most of the acreage that isnt is Cardinals territory because southern Illinois is closer to St. Louis than Chicago. Large parts of Indiana and Iowa are also Cubs territory. The Chicago Cubs fans wear blue Chicago Cubs hats and also Chicago Cubs shirts to support the team.
And this is because of the Cubs long history of airing games on WGN. WGN was widely available across the US on cable as early as the 1980s. The only other team with a comparable TV footprint was the Braves whose games aired on TBS. (The Braves were in fact owned by TBS for a while.) So people all over the country could watch the vast majority of Cubs games, at a time when most baseball games were only televised locally, if at all.
Thus the Cubs have a much larger and geographically dispersed fan base. In contrast, the vast majority of White Sox fans are concentrated in a certain portion of the Chicago area.