I've heard about the scientists supposedly disproving the simulation theory. I guess I just think that if someone were advanced enough to create our universe and the life within it, they would also be able to prevent us from discovering that it is indeed a simulation.
Also, I believe your article refers only to *computer* simulation, which is quite different from real, physical lab-grown universes. And who knows what else we might not be able to comprehend in regards to how a universe can be created.
The multiverse theory is just a theory. It's not accepted, at all. So far proof for it is quite lacking. But we should expect as much. The thing is, multiverses are what scientists need to prove to get people to accept that our universe was just an accident. If we're the only universe that exists, it is very strange and coincidental that our universe has the building blocks for life to exist, life which can even ask these very questions. I've read that the chances of such a universe existing is very minuscule. Yet in the multiverse theory, the chances of us NOT existing is minuscule, because anything that can exist, will eventually exist, in some other universe.
So that brings me to your question about the big bang. In the multiverse theory, nothing is needed to cause the big bang, because a vacuum of 'nothing' always has fluctuations of energy popping in and out of existence. Scientists have even discovered certain particles that time travel at brief intervals. Any kind of universe will exist, no matter how small of a chance it has to exist. Think of each fluctuation of energy as a 'universe'. Some universes exist for less than than a second, much less in fact. Others might have tiny bits of matter in them, or even matter in the negatives.
I strongly recommend reading Lawrence Krauss' "A Universe From Nothing: Why there is something rather than nothing". He talks about all these things. He also gives scientific proof that our universe is made of ZERO energy, since there are positive and negative energies scattered throughout the universe, and the strong consensus is that they balance out to a big, fat ZERO.
But essentially, without a multiverse, we have no earthly idea what would have caused the big bang, and certainly not a big bang that's strong enough to create something as special as the universe we call home.