The Cure's 2019 headline set saw the crowd thin noticeably sometime about 1/3 to 1/2 through the set. It was one for the ages, but there were still plenty of people who turned up to check out a few tunes, weren't feeling it and wandered off for alternative entertainment. The Who, last time they played, saw a big dip in crowd size in the same way. To be honest I wished I'd wandered off for better entertainment that night myself, but grimly stuck with it out of some sunk cost fallacy in my head that things would pick up.
I legged it about 75% of the way through Jungle this year knowing I could make it to catch the end of Dua while the paths were clear. It wasn't because Jungle were bad, but more a bit of FOMO meaning I thought the crescendo of Dua's set would be worth catching and it was just a 3 minute run away.
I could be wrong but if The 1975 are headlining the Pyramid Stage and Loyle Carner is headlining the Other Stage on Friday night, other areas may experience overcrowding, as I don't think either act will attract much of an audience beyond their existing fans.