I have looked at this issue for nearly 35 years. There are a number of problems that must be taken into account:
##I. BIG BANG CENTER
First, we did not see the beginning of our universe take place. There are no eyewitnesses that can tell us what actually happened. Therefore, it is a many billions of years old COLD case. In other words everything we put forward regarding the beginning of the universe will always be only speculation. We have no way to prove anything that we hypothesize regarding how are universe commenced (no matter how many theories are proposed regarding the beginning of the universe nor how good they and their corresponding math equations appear to be, there is no way to fully test them to prove out anything they make claims for).
The real world frame of reference for our universe is three dimensional plus time. The visible universe is not uniform in all directions. That is all the galaxies, etc. are not uniformly spaced. Since, supposedly the Big Bang started with a very tiny singularity blob (at least for this theory), smaller than a marble, then there ought to be verious vector trails (even if they are fragmented or somewhat askew, blurred or dissipated) of some sort going back to the marble size singularity state (especially since matter across our universe is not uniformly spaced along its x, y & z axis).
Since matter is not uniformly distributed across the universe then there had to be other forces at work to drive their uneven distribution. There ought to be somewhere along the "edge" of the visible universe signs and traces of splitting of matter and clumps of energy even if we can't see the actual center (point) of where the Big Bang originated. That is even if space can expand separate fron the matter and energy it contains, having started at a point no larger than a marble, it must have vector changes at some point as matter and clumps of energy split off at uneven intervals and directions.
Even if inflation did occur (not so sure that it did) by the time that period ended changes in forces and corresdponding events had to occur that should have eventually caused its effects to become visible somewhere around and along some part of the edge of the visible universe. In other words, at some point(s) matter & energy had to change direction to leave large gaps of space between them, especially since there is an uneven distribution of matter and energy clumps. I doubt that all these changes suddenly ended by the time they became part of the visible universe.
Two dimensional demonstations lack ability to show true three dimensional effect regarding starting at a tiny point to espansion of 13.7 billion light years (especially since it is in fact spherical that started at a tiny point). In other words, if we look across through our universe sphere (not a two dimensional plane) somewhere at least near the edge of our visible universe we should see at least some large area where galaxies are much closer together compared to say an eight billion light years area around where our galaxy is located now (certainly if the universe had a tiny starting point there has to be a visible change somewhere in an espansion covering a huge area of more than 13.7 billion light years).
##II. CONCLUSION
There are many other Big Bang theory claims that I believe have problems that indicate that the Big Bang either is not the cause of our universe or we are nowhere near understanding how the beginning could have happened. In any case we will never be able to prove what brought the universe into existence. We would have to be able to travel all the way back to the ouside of the universe where we could observe it all taking place in real time, which is impossible to do.