A much stronger argument for the chocolate cake would be that there must be some incredibly small probability that atoms would be come together by chance to form a chocolate cake in the asteroid belt. However, all physical possibilities are real, according to the argument for many worlds. Therefore there is actually a chocolate cake in the asteroid belt. It just happens to be very distant from our blob of amplitude.

A similar case: there must be a world where your arm transforms into a blue tentacle, even if this world has an incredibly small amount of amplitude. Granted that you don't expect to see this happen, there is still a different version of Eliezer who does see it happen. Of course, as you have argued, he cannot explain it. But what do you think he says about it when people ask why it happened? Does he begin to believe in magic?