It's not that deep. Yay is one of vals most popular players and that's why he had a lot of haters/people clowning on him when he fell off. More popularity equals more 'haters' that's pretty much it.
I think the 'he was abusing a broken agent' is a cheap argument, yay was mechanically excellent back then. His game sense was great, his aim was great. But he mechanically fell off and didn't expand his agent pool after the Chamber meta. Hope he can redeem himself when he returns.