Let's take a simplified analogue - news in TV screen. If you switch TV in then it does not start from "singularity", it starts from fully running scene. But it looks like a big bang on TV screen. Let it be "light and forms there" if we talk symbolically.

There are no traces on the screen about what was before the screen was switched in. There are traces about what was before, but they are outside the screen, They are with the TV station, If you go there to stream them, you can see what was happening before the "big bang" on the screen.