I just came up with a theory. Well, barely. Speculation. An idea. I was thinking in horror movie terms and that people aren’t always who they think they are. If Doctor Whale being Frankenstein was too easy, what if it wasn’t? I can’t remember if Rumple called Whale victor in Storybrooke, but if he didn’t? What if Whale is not victor, but his brother? Whale is he monster. He killed his brother. They’re twins. Whale is tricking everyone.
Gold Definetly called Whale “Victor” in the pawn shop at the end.