I believe the big bang theory started out as something called the “cosmic egg”. It was originally an idea proposed by Georges Lemaitre, a Belgian Roman Catholic priest, who was also an astronomer:
http://www.physicsoftheuniverse.com/scientists_lemaitre.html
Personally, I think the idea of the entire universe starting out as a singular super condensed blob, is absolutely ridiculous.
When God SPOKE his creation into existence, I've often wondered what that would look like. In one moment there was nothing, in the next moment there was EVERYTHING (in terms of matter anyway).
Any explosion of energy - call it a Big Bang - works for me...
It's not that a multiverse doesn't require a Creator. It's that the argument for a multiverse means that the fact our universe seems to be "tuned" for life is simply an accident. It's one of many universes in the multiverse. We simply hit the cosmic jackpot. Thus the appearance that the universe seems "designed" is merely an illusion. The existence of the multiverse cuts the ground out from under the argument that our apparently designed universe needs a Designer.
Keep in mind that no one has ever proven the existence of the multiverse. The concept was created solely to avoid the logical conclusions from the apparent design of the only universe we know.