A festival lineup isn't simply a list of someone's favorite artists. There are :
Budgets.
Availability.
Artist fees.
Travel.
Genre.
Audience expectations.
Scheduling.
Sometimes complicated negotiations, one artist might only be available on a certain day, another might already have a show nearby, two artists might not want overlapping sets. Then everything has to fit into one schedule.
The lineup you see is the final result of dozens of decisions most people never hear about.