> Clearly there would be a significant IQ difference between the average sports fan and the an average D&D player.
Really? What do you base that claim on? The fact that lots of "geeky" people play D&D doesn't mean that the average person playing D&D is actually smarter than the average sports fan. In college I knew some smart people who played D&D, but I knew some dumb people who played it, too.
The people I knew in college who watched sports were also in college...
Also, attending college does not guarantee that one is above average intelligence. The average intelligence of college attendees is higher than the average intelligence of all adults, but there are certainly some college attendees with below-average intelligence.
If you are comparing fans of esports vs. D&D players, that gap would probably be narrow to non-existent.