Yes that USF figure is skewed, but it makes me wonder how many "tavern 'noles" would jump behind USF if they got bumped up to the Big 12. I am starting to warm up to the idea of adding USF and UCF as members 13 & 14 or even 15 & 16. I don't think they fit the criteria for the primary targets for expansion, but could be nice additions after whichever schools end up being 11 & 12.
Some people downplay game attendance, buy IMO it is a pretty big indicator how invested an alumni base is in their athletic programs. And I am including all sports, because the athletic department budget for Big12 vs. ACC programs is at least $30M higher. That is a lot of ticket sales and sponsorship revenue to make up.
I would doubt "Tavern Noles" would jump from FSU to USF/UCF if they gained Big12 membership. Especially, the "Tavern Noles" that count, those that currently buying FSU season tickets. It's not like FSU is a 7-8 win program like Iowa. FSU consistently wins 10+ games and playoff team.
The other dynamic is Iowa does not have professional sports teams or theme parks in the area to fight for people's entertainment dollars. Being a college football fan isn't cheap- with the cost of two tickets (plus possible donation) easily in the $1,000-$2,000 range.
BYU is the only team Big12 ready from the financial and entirety of athletic programs perspective. All the other programs have potential. In that respect there is no urgency to add a UConn, Cincy, Houston, CSU, etc. The Big 12 can wait until the current TV contract is up for renewal as the above teams (other than UConn to ACC) will not be invited to join the Big 10, ACC, SEC or Pac12 any time soon.