"Most scientists absolutely state that they cannot know anything that preceded the big bang."
Yes, that is what they state. That is very different from stating that there is nothing that preceded the big bang, which is what you said they say.
But never mind.
Both are true. They believe there was no "time" at that "time." Therefore, they both cannot know, and they believe it was impossible for anything to preexist in any sense that we can understand. It's not a whatever point, the whole point is where did all this come from and why. Science can't answer that and sometimes says it doesn't want to. But then when science started the conversation, I thought they were explaining everything and dismissing a First Principle based on their empirical data. The fact is their knowledge collapses into mystery at all levels, and they say those mysteries are unknowable and unobservable. Is there a God? Is this all random? I don't know but they certainly don't know, either.
On evolution, a much smaller subject, I think evolution has occured and science may ultimately find all of its mechanisms. I find it interesting they haven't yet. But the real question is why did life form why does it evolve why is there intelligence, etc. Maybe for a reason or cause beyond randomness.