Yes I’d seen that, however they’re back in the USA for 2 gigs on the 21st & 22nd June so it must be doubtful they’re be returning to the UK after having just left.
A combination of a few factors. Being on the Sunday doesn't help, especially when England are playing that day in a knock out game and Glasto isn't showing it. Her fans were unable to buy tickets (part of the glasto charm but not helpful for a more niche headliner), the rest of the lineup leading up to her weren't inspiring people to stay. Despite the attempts to make the festival more diverse, the crowd is still mostly white and guitar bands will be more popular headliners than R&B, rap etc. Add it all together and you get a very small crowd.
They don't seem interested in sorting it out properly - which is a full reconfiguration.
Silver Hayes has helped but its clearly not enough
edit: not to mention ridiculous bookings like bicep