For all universal matter to have “simply come into existence” denotes that there is an unknown science beyond our conventional and observational “cause and effect” newtonian and quantum theoried physics as we understand it now. What we perceive now in the universe are the cause and effects that have since progressed, as described by our sciences, from the “genesis” of that PRIMARY imposition of some sort of grand primordial “somethingness” into the grand primordial “nothingness”.
There is both math and observation to support the big bang theory, but the impetus of creation relies on some ‘kickstart’ from The Creator. If I read your post correctly I think we are saying the same thing.