I think the author is not really looking deep enough. I mean, look at Batman and James Bond. They’re both mortal men who use a bunch of high tech gadgetry and cool cars to take on supervillains. Only difference is one wears a tuxedo, and the other wears a cowl. Yet James Bond is considered an icon of cool, not a representative of a genre only considered suitable for children.
And as others have pointed out, there’s precious little difference between being a fantasy sports player and playing other games based on fantasy. At least with the other games, they’re honest about the fantastic part, and not trying to cloak it in whatever respectability professional sports has.
I also think the rise of “nerdy” stuff is a sign of a set of cultural shifts- the Internet connecting people who do actually like this stuff, but were afraid to speak out and people having children later, and having the time and money to indulge in this stuff. I suspect a lot more people have liked this stuff all along, but just never really had a way to connect with anyone else who did.
Hell, just look at the box office success of prior superhero movies for proof- the 1978 Superman and 1989 Batman movies cleaned house and spawned several sequels each. The main thing is that the Marvel universe was essentially unexplored in cinema until the 21st century. (think about how many Superman and Batman films, TV shows and what-not there have been over the years?)
As for the having kids later, most people really get into their nerdy fandoms in their 20s, and if you were having kids and becoming parents in your early 20s, people probably just didn’t have time for it back in the day. I know that even having had children in my 30s, my videogaming, nerdy movie watching and general engagement with the nerdy universe is a LOT lower than it had been prior to children. I suspect that if it had happened right when I got out of college or even before, I’d have had to build that anew as an adult, and in the face of whatever competing leisure activities I’d got used to in the intervening decade while raising the kids.
It’s not a competition with sports fans, and I don’t think it’s really that it’s a matter of jocks vs. nerds. It’s more that the nerds were always there, but due to inadequate communication and other societal factors, they weren’t able to effectively concentrate themselves and make their presence and desires known.