The Motive

Multiverse theory is actually a set of theories, all proposing that there are more universes than ours (or beyond what we can observe, in one case). They are all attempts at explaining how special our universe is. Why are physical laws configured just how they are so that atoms can form? Why would the Big Bang model place Earth at the center of the Universe?

What supporters will admit is that multiverse theories are an attempt to explain how our universe, which is so specially configured for life, could exist by chance (without God). The thing no one wants to say out loud on the atheist side is that all of the fine-tuning in the Universe is extraordinary evidence for special creation by a supreme being, which is the very reason they feel the need to find an alternative.

The Problems

1. There would be no real way to find out if there are other universes.
2. From a philosophical point of view, the presence of other universes wouldn't generally answer anything. If we wonder how our universe got here, we would have to wonder the same for them.
3. It actually fails to address the issue of the extremely low odds that our universe would be the way that it is. It is merely the assumption that an extraodinary result means many attempts were made, which has been dubbed the inverse gambler's fallacy.

God of the Gaps?

Wouldn't appealing to God be a “God of the gaps” situation though? In other words, is God only used as the answer because some people want God to exist and insert him wherever they can? That would be the case if there was no indication in the evidence of what the cause of the Universe was, but that is not our situation. Instead, the extreme fine-tuning for life indicates deliberate action from an intelligent being.

We understand this in everyday life all the time: Sure, unlikely things can happen sometimes, like a meteor coming through the roof of your house, but improbable things with clearly intentional results are almost never the results of chance. Your friend who never passed a math exam did not just luck out when he got 100% in an large, hand-written exam all of a sudden. Still less would the creation of the entire universe in all its intricacy happen without an intentional act, especially when you consider how unique in it we as humans are.