Like the theory of evolution, the big bang idea is a bunch of bullshit which is mainly being defended by academic dead wood. The idea of multiple universes is mainly motivated by a clear understanding of the laws of probability and what the odds are against evolution and evoloserism in the one universe we actually have in real life.
I’ve watched for years and years as these folks come up with one theory to explain the failures of another theory. I watched these folks pass theory as fact when pushing another theory. I watched the same folks keep trying to push a universe with boundaries, multiple universes, other dimensions, etc...., and of course discuss it as though it is fact - AND get funded for it handsomely - while real scientists doing actual experiments “in situ” get the crumbs. (Most of the funding is from government - just another form of welfare and dependency that undermines those doing real work.) And these same real scientists don’t get defensive when in many cases - they too are still stuck with theories in some cases.
In my opinion, these “theoretical” folks who can’t get past theory but talk like they have are simply insecure people.
I for one have no insecurities over the possibility that our universe IS the only one and has literally no beginning, end or border. I am not surprised when a new telescope shows more stars behind known stars - nor will I be surprised when the generation telescope shows more behind those ad nauseum - n++;
Down to earth people like real scientists are very secure in their being.