Physicist Sir Roger Penrose, who has worked on expanding Einstein’s theory of general relativity proposes multiple big bangs might have lead to where we are. Called “Conformal Cyclical Cosmology”. Personally I find this more plausible, but then again I’m a layman.
This would much better explain why the universe isn’t a symmetrical curve from a common center. If more exotic or even less common elements existed soon after the occurrence of the Big Bang this could have lead to more smaller bangs (or even bigger bangs possibly?) Being in a much denser and warmer state than now I think it’s entirely possible.
If Penrose is right, and I’m not saying he is, then theoretically our universe should explode and form into another universe at some point. So is dark matter leftovers from a former universe that has been flung around by other big bangs? Incomprehensibly wild stuff to me, but I enjoy thinking about it.