Vansh has said in many occasions that Riddhima is just a messager. He always knew Riddhima was upto something. In episode 51 he says that Riddhima is a medium to reach her partner and someone is behind her. That's why Vansh paid Ishani's fiancee to figure it out.
So I guess Vansh needed to fake his dead to figure out who is Vansh's opponent. Vansh is always ahead of all. He knew that Riddhima wanted to save Ragini from him, and still he didn't question Riddhima? That means he must have figured out something. He knew that the real culprit will show his face when Vansh is dead. Now he wants to play his real game against Kabir. Vansh is playing chess, where Riddhima will be a piece of his game. Similar to Kabir needed Riddhima for his game.
I hope this is the way the story goes. Cause this way Vansh will remain the most iconic smartass persona ever!