I think there's no must. It's just one possibility that agrees with the general theory of relativity and the astronomical observations we have made so far. Two notable observations that have led to the widespread belief that at some point a big bang has happened were Hubble's observation that the universe is expanding and cosmic background radiation. No one knows what can happen in future.
I posted this quotation because it is interesting, just as your comments are also interesting.
Sometimes the weirdest statements must be accepted as scientific.
This is actually an extended version of Creationism.
I think Universe does not undergo our limited ability to perceive time.
Einstein has been one of the worst fathers in history. A good father is in any case better than 100 infantile scientists.
Universe may also be an endless circle.
You definitely understand why I posted this quotation.
We don't have to believe it or even agree with it, but it does suggest an interesting possibility, and it makes us think.
Unfortunately, we'll never know the answer, but it's fun to ponder it.
Thank you for your intelligent comments.