Consider the Schroedinger Cat experiment again, within the context of the Many Worlds (MW, or MV) interpretation.

We are in Reality B where the cat is described by superposition ψa+Ψd . Call this the initial assumption iA. However:

By the assumption of MV, as soon as the experiment was turned on and the cat was described by ψa+Ψd, reality splits in two, into a Reality A and Reality D where there is no contradiction: In A, the cat is alive ψa, and in D, the cat is dead Ψd. The key here is that even before the person in both A and B open the box, the cat is NOT in a superposition. Before he opens the box, the cat is objectively either alive or it is dead.

So the MV interpretation of Quantum Theory implies that a superposition is not really a superposition at all. There is ZERO time when the cat is both alive and dead. Reality immediately splits, removes the contradiction, and -- this is the key -- creates two realities where the laws of Quantum Theory are de-validated.

The Laws of Quantum Mechanics is destroyed by the Multi-Verse hypothesis. That is, the MV hypothesis contradicts Quantum Theory.