So here's my theory.. Originally Snoke was intended to be Plagues. Then JJ decided the new trilogy needed a big twist. They jettisoned the original design, (hence the different look in concept art) and decided to make him Vader.
Vader didn't die in ROTJ. Luke secretly saved him and and together they started a new Jedi training place thingy. Vader in the background, operating in the shadows type stuff. Dad is still kinda dark side and still believes in bringing order to the Galaxy. He goes back to his old ways and seduces young Ben Solo to the dark side. They betray Luke. Luke feels responsible for failing as a Jedi teacher and for being fooled by his father. He goes into hiding. 30 years of dark side force use turns Vader into this:
So yeah... First and last article. Just a thought.