The so-called big bang theory directly proves that the universe has been expanding in the past, so it must have started from infinity. And completely ruled out that the universe once shrunk to a limited volume and then expanded to today (bouncing model).
Hubble's law only shows that the universe is expanding now, and the past of the universe has no limit. So Hubble's law is not evidence of the big bang. It is only the smallest part of the evidence-the derivative of the current universe volume is greater than zero. It is precisely because there are too many people who answer Hubble's law that people think that the theory of astrophysics is completely unreliable. This is absolutely wrong. The big bang theory is derived from strict mathematics.