Make no mistake, the Big Bang is unpopular in many quarters and an exterminator has long been sought. The trouble is, an infinite regress of this universe is logically untenable because everything—including the demise of the universe before our time—would already have happened. And there is no evidence for previous universes that gave rise to this one and disappeared.
If you still want to invoke the Big Bang, the only answer you can give is, “well, the Universe must have been born that way, and there is no reason why.” But in physics, that’s akin to throwing up your hands in surrender. Instead, there’s another approach: to concoct a mechanism that could explain those observed properties, while reproducing all the successes of the Big Bang, and still making new predictions about phenomena we could observe that differ from the conventional Big Bang.Ethan Siegel, “If the Big Bang wasn’t the beginning, what was it?” at Forbes
He goes on to argue for cosmic inflation theory, which has quite a few problems of its own.
Here’s the problem: The explanation for an event may be outside the event. In that case, one can’t derive an explanation from within the event. If we had never heard of William Shakespeare and came across a bandshell production of Hamlet, where all the people onstage are speaking in Elizabethan English, listening to them would not tell us that Hamlet is his best-known play. Someone outside the play would need to tell us that. The characters, in their roles, don’t know it. All ultimate origins are probably like that. We may get some hints but we will not get regress. Understanding Hamlet will not enable us to communicate with Shakespeare.
See also: The Big Bang: Put simply, the facts are wrong.