We moved the date a week later so that there's some time to get set up after the fair ends. For the last few years the week immediately after the fair has been our setup week, and it's when our parking and registration teams and early arrivals show up.
The fairgrounds staff is trying to clean up / move equipment / mow grass on the heels of having a quarter of a million people (REALLY!) at the fair, and at the same time set up electrical and water lines, tables and chairs, and other items for us. It's a killer turnaround.
Next year the date one week later was available, and we jumped on it.