It is fun to follow these "who did it" debates... I mean, "All are me and I am all" Vitiate literally can actually be Ragnos or Kressh or Dahkan at this point. There is no limit to his alter egos anymore. Ragnos doesn't care he has a body or not, unlike Vitiate who wears them like clothes, and he just keeps on ruling as a spirit. Hey others did as a head in a jar, so whatever works for him. Other Sith and generations had the opposite even, Now, what is Kressh or Dahkan's kick?
Heh, there's a period between the Battle of Korriban and the time in which the invading Republic forces were temporarily repulsed from Sith Space (per the Guide) where there were possibly at least 5 different competing Dark Lords/Actings/claimants/usurpers: Sadow, Kressh, Dakhan, Lord Vitiate, ghost Ragnos, and any other factions or remnants that escaped the Fall.