GT can't fill up its stadium with alums or even strong current GT fans. We have to broaden are appeal to current non-GT fans that live in Atlanta. It is a huge market. Atlanta United has shown there are a ton of non-traditional sports fans in the area. Once we do that, THEN we can complain about the other team buying up too many tickets. At this point, there is a glut of tickets on the secondary market at usually cheap prices.
Also, visiting fans are an issue in many football games especially in the NFL. I think many fans see it as special event. The opportunities can be limited so many fans take it as a chance for a vacation or even bucket list thing. You combine that with the fact that Atlanta has a ton of transplants that end up here from all over the country and that graduated from colleges all over the country. That all means there was a lot of pent up demand from the UCF fanbase to attend a game at BDS.
Lastly, of course a winning and top 25 team will help this dynamic. The people that currently sell their tickets are more likely to use them if they like the product.