And believing that it is unavoidable even though it is not observed:
If you accept that inflation is a stage that occurred in the Universe’s past prior to the hot Big Bang, and that the Universe itself is inherently quantum in nature, the existence of a multiverse is unavoidable. Even though we cannot observe these other Universes, we can observe a huge amount of evidence for inflation, indirectly pointing to its inevitability. We can also observe a huge amount of evidence that the Universe itself is quantum, even though we have no proof that inflation itself behaves as a quantum field. If you put these pieces together, it unambiguously leads to the prediction that our Universe should be only one of countlessly many Universes, all embedded in an eternally inflating, expanding background. One Universe is not enough. Even though we cannot detect it, the prediction of a multiverse is unavoidable.Ethan Siegel, “One Universe Is Not Enough” at Forbes
It’s becoming obvious that post-modern science will have its multiverse irrespective of evidence from nature and will prefer it and its component beliefs to evidence from nature. That is why some of us think that the multiverse is science’s assisted suicide.
See also: Startling admission about the science (i.e., non-science) basis for the multiverse (cf. Ethan Siegel)
Science writer Ethan Siegel says, the multiverse is not the answer
Sabine Hossenfelder: The multiverse is “a fringe idea”
What becomes of science when the evidence does not matter?
The multiverse is science’s assisted suicide