Who started “2023 Mid-Season Invitational”?

Riot Games, on Open web, May 2, 2023. It reached 2 platforms in 3 weeks.

LineageKey steps, 6 of 9. Lines follow time and platform
Riot GamesBefore the first postThe kick-off: 2023 MSI Play-Ins Day 1 recapRiot GamesFirst postPressOwner responseObserved peakPressPatient zero