All Festivals book acts that they think will sell tickets. Some will have a higher influx of foreign customers than others and book accordingly. Take Hurricane Festival for example. Sam Fender is playing there, but 4th down with the 2nd and 3rd acts on the hill being German. Makes perfect sense.
I think that must be them all, I've only got those names too, hope there's some other good stuff on the undercard too as quite promising for me so far!
Glasto is a unique festival where tickets are sold prior to the lineup, and where lots of repeat visitors got the ticket sales process to their advantage with syndicates and such. Comparing it to Coachella is totally braindead in that context. It also means the festival cannot use the same booking metrics that other fests use. It's not rocket science.