The Multiverse Theory is the unscientific and anti-scientific idea that the exquisite design in our universe isn’t caused by an intelligent designer (i.e., God), but it exists merely because there are an infinite number of universes and we just happen to be in one that appears to be designed. Yes, it is laughable, but the continually growing evidence for design has forced people to come up with a non-God explanation.
Their theory is a self-contradictory attempt to move the goalposts. Even if more than one universe existed, let alone an infinite number, that would just give greater evidence to the design theory. More complex things means more evidence for a creator.
I think that those who know that support for Darwinism is crumbling use the Multiverse Theory as a placeholder until they can think of something which is at least a little more plausible.
See The Multiverse is the Poker Player’s Best Friend for a good illustration. Here’s a sample:
A couple of years ago I trotted out the “highly improbable things happen all the time” meme our Darwinist friends use to such advantage at my home poker game. For those who don’t recall, this is what happened. I dealt myself a royal flush in spades for the first 13 hands. When my friends objected I said, “Lookit, your intuition has led you astray. You are inferring design — that is to say that I’m cheating — simply on the basis of the low probability of this sequence of events. But don’t you understand that the odds of me receiving 13 royal flushes in spades in a row are exactly the same as me receiving any other 13 hands. In the game we are playing there are 2,598,960 possible hands. The odds of receiving a straight flush in spades are therefore 1 in 2,598,960. But the odds of receiving ANY hand are exactly the same, 1 in 2,598,960. The odds of a series of events are the product of the odds of all of the events. Therefore the odds of receiving 13 royal flushes in spades in a row are about 2.74^-71. But the odds of receiving ANY series of 13 hands is exactly the same, 2.74^-71.”