In the past few years, Festival of the Arts has debuted the weekend after marathon weekend. In 2020, I stayed from marathon weekend until the following Sunday, so I could catch opening day of FotA on that Saturday.
The first day of the festival brings pretty big crowds, including armies of vloggers. I can't imagine them wanting to run that in the middle of marathon weekend, or have CMs try to island hop across world showcase to bring fresh food from backstage to the festival booths mid-race!