Banksy has been active since the 90s, definitely already famous in the 00s
It's got just the right mix of highbrow disdain, unironic self righteousness and naughty language to titillate the average guardian reader though.
(Also, if you're familiar with Charlie Brooker's output, he's not really a 'highbrow' type. He started out in games journalism.)
He got more famous and acclaimed since black mirror.
At the same time it's painfully obvious it riled him up being a more obscure and less famous equivalent of banksy.
- Creator of Black Mirror, 5 years before series premiere