For me the first mistake he made at glasto was the stage set up....the lighting was ridiculous and to me it seemed like he was trying to make a music video rather than a festival gig....
Second was his attitude....he never engaged with the crowd, didn't thanked them for showing up, didn't make any light of the backlash against him....he was too cool for all that....he showed his ego, nothing else....
After that, his set list just wasn't strong enough to headline a festival...and he can't sing for sh1t so don't know why he even bothered....
Kanye headlining Glasto was just another sad example of how celebrity is more important than talent these days...