For acts that tour occasionally like t4f, there's always better money than Glastonbury offers available to them. And cos they only tour occasionally they'll be wanting the best money.
He absolutely can be a prat (his most recent behaviour really got my goat, although I do appreciate his proper apology for it on reddit) but are people really moaning about him playing up at an awards show or other similar behaviour?
What a bland state of affairs we're at where people complain about that kind of silliness. Either much much worse has been done by the complainers' favourite artists or we are really demanding an embarrassingly high bar for behaviour in an industry that is built on mad people doing mad sh*t, and it actually being quite entertaining. The alternative is all frontmen are like Chris Martin. At least Healy makes good copy.