I'm guessing because it's "Jersey Week" when most New Jersey Schools have a fall break. Sunday would be much better (at least I'd have to think so) as weekends (so far) have been less busy at Epic compared to weekdays. Sunday is a big travel day and lot of people aren't going to use their one Epic day on a partial park day.
Thus far Sundays have been the slowest day at Epic, generally. (Sunday is Nov 2nd).
Despite that being "Jersey Week," it's really been a nice time to travel, crowd wise & weather wise. I've done that week or the preceding several times.