Plagueis' absence as a living character in the previous six films presents an interesting conundrum.The_Lhc said:if he's been around all this time it would tend to contradict Yoda's assertion regarding the Sith: always two there are, master and an apprentice. That's the Emperor and Vader for the most part, if plagueis had been hanging around in the background that would make three.
I'm reaching a little here, but go with me...
From what little we know of Plagueis, he was so powerful with the force that he could cheat death.
I'm oddly reminded of The Exorcist III, in which the Gemini Killer (who was possessed, accounting for his murderous behaviour) is reanimated years after his body was buried.
The possessing demon willed the host's body back to life; but this took decades. This was a kind of agonisingly hard won, unholy resurrection.
After Palpatine "murdered" him, Plagueis may have slowly reanimated, initially through residual force consciousness, incrementally but inexorably gaining strength.
This would mean Plagueis remained omnipresent through the previous six films, if never intervening as an animated Sith presence, thereby preserving the "rule of two."
Even the name Plagueis suggests a nagging pestilence that might be fought off, but can mutate and resurface.
Since the Star Wars franchise is inherently silly, and we accept the presence of ghosts and mystical powers and creatures, I quite like this idea.
This would make Snoke a zombie Sith Lord, and the most powerful exponent of dark side powers in the entire Star Wars canon.
The name "Snoke" lacks the menace of Darth Plagueis, but it works as a cover, where an outwardly ineffectual, unthreatening persona is a front for genuine malevolence. (Think of Snoke as Star Wars' take on BoJo.)
I guess Snoke could be a ghost, but then why appear as a hologram?