There have been a lot of stories dealing with parallel universes. In past years, TV shows like Sliders, Stargate-SG1, Star Trek, Fringe, Doctor Who and many others have played with the idea of universes of infinite possibilities. Other mediums would include the video game Bioshock Infinite or most comic books. These science-fiction stories are interesting and show a variety of creativity in ‘what if’ stories like having Leonard Nimoy in a Goatee!
There are many different theories that can all be called ‘the multiverse theory,’ but the basic concept they all have in common is that we live in one of many (or infinite) universes. These universes have different rules, physics, and/or choices made in them. These many infinite universes remove the need for a designer because we just live in the one that got things right. It’s the blind watchmaker theory at a universal scale.
Now while it is only a theory from theoretical physics, there are some issues with it in regards to being a contender:
- Either the multiverse would be infinite or it would have an origin event. If it has an origin event that needs to be explained, it would fall subject to the Kalam. The multiverse cannot be infinite as you cannot cross infinity.
- The multiverse cannot be proved or falsified. This makes it a ‘multiverse-of-the-gaps’:
“There will be no way for us to detect these universes by any experiment. And so, for the non-theist who wants to deny the existence of God because of a perceived scarcity of experimental evidence, the multiverse has to be very tough to swallow. Belief in the multiverse requires a leap of faith beyond science and into the realm of metaphysics”. 
- The multiverse itself would need to be fine tuned:
“The skeptic must assume that the multiverse necessarily generates an evenly distributed combination of universes that have the many different possible sets of physical laws. This specific outcome would require that the multiverse, itself, be finely-tuned for the specifically required outcome. Instead, if the multiverse were not finely-tuned, stasis of all “settings” would be the natural state of the multiverse, and it would naturally only produce universes consistent with that static set of settings. Since there are orders of magnitude more combinations of physical laws that are hostile to life, the probabilities that the “correct” settings (for life) would be the natural one at the multiverse’s state of stasis reintroduces the teleological problems attempted to be resolved in this universe. The fine-tuning has not been removed, it has merely been shifted from this universe to the multiverse”. 
- The theory can be reduced to the absurd by.
The existence of Pink Unicorns:
“Since we know that horses are possible, and that pink animals are possible, and that horned animals are possible, then there is no logical reason why pink unicorns are not possible entities. Ergo, if infinite universes exist, then pink unicorns must necessarily exist.” 
The existence of Boltzmann Brains:
It is more likely for a single brain to appear into existence than a fine-tuned universe or multiverse to do the same. If that is the case, everything would be an illusion.
The existence of Intelligent simulations:
“We cannot use the argument that the physics in our universe leads to multiple universes, because it also leads to a fake universe with fake physics.” That undermines the whole argument that fundamental physics generates multiple universes, because the reasoning collapses in circularity” 
While these are only some of the basics on this topic, the multiverse may just be in the realm of science fiction rather than an answer to why things are so designed for life.