Back in around 2015-2018, Riot was on a crusade against AP off-meta builds, hard nerfing things like AP Tristana, AP Sion, AP Alistar, AP MF and many similar builds despite having low pick/winrates.

Then in 2019 they made a full 180 turn, starting with the Nautilus AP ratio buffs, followed by Malphite AP ratio buffs, Kog'Maw AP ratio buffs, Shaco, Varus, Twitch etc. and now Xin is next.