Here's what I'm thinking. Snoke is indeed Darth Vader, or at least the image of him. Anakin Skywalker did indeed die in Episode 6 but the legend of Darth Vader lived on.
No doubt, Ben Solo would have heard about his grandfather, the good and the bad stories. There would have been no way to avoid it. He would have also known that every Jedi needs a master. If he gave in to the dark side, he would either need a master or an apprentice because there is never just one Sith Lord.
Could he not have created the Master to guide him himself? I believe Snokes is a manifestation by Kylo Ren of his hero, his own grandfather, Darth Vader. He brought him back to 'life' to give himself a master. He may have done this subconsciously to fulfill what he thinks he must be, the student to a great Dark Lord.
I don't believe there were that many Dark Lords left after the Return of the Jedi so this may have been the only way to have someone in that Master role.
But, correct me if I'm wrong, but doesn't the apprentice have to kill the master in order to become the master himself? Would this lead to a show down between Kylo Ren and Snokes (Manifestation of Darth Vader). That could be interesting.