One with the same evidence as "god did it."
> is not a theory and it makes no testable predictions.
This is true of the multiverse too. It is an attempt to explain why things are like they are rather than a testable theory.
Okay, this is just going in circles. Up above you accepted that multiverse theories did make testable predictions. And they do, which is what makes them science.
edit let's use a concrete example. This thread is about the cosmological constant. I could easily say that concept is causes by multiverse influence on this universe, just as rightly I could say it's god's finger on the scales. Neither now have experimental data because I can say that.
further edit sorry, this is a bit stuck in my head. Look here
https://en.wikipedia.org/wiki/Multiverse
Notice that it is labeled a hypothesis, and the theories that involve evidence predict a multiverse may be possible with these conditions.
"For some reason" is not a theory and it makes no testable predictions.