I have never seen a good proof anywhere that every outcome of a choice that can occur, does occur. Sounds to me like its wishful thinking on the part of the physicists ever eager for funding.

But there is a fundamental flaw in ,multiverse theory. If every possibility occurs in some universe, then its natural that in some universes bad things happen. Whats the point in trying to stop that from happening, since that possibility has already been taken by another universe?