Tbf I wasn't going so far back as to when Robbie was at his peak so much as a couple of years back.
Still, he headlined Isle of Wight last year and was positively received. And as noted, Glastonbury has moved on from a more indie-focused feel so is more amiable to pop headliners. We're certainly a long way from Jay-Z headlining Glastonbury being treated as like it was some grand offence.
The movie industry is embracing weird sh*t. Pharrell Williams' biopic that come out today that has his life depicted in Lego has a really odd feel to it as a concept.