If I were an atheist, I would probably reject big-bang cosmology, which assumes the universe had a beginning, and opt for the universe being eternal. However, I’d also know in my conscience how intellectually untenable that is.

Since it’s demonstrated through observation and assessment that every object in the matter-space-time continuum has a cause, it’s logical that the physical universe itself has a cause: Something transcending matter-space-time must be the cause of this universe.

If you don’t want to call that unseen Cause God, that is your prerogative; but we cannot deny its existence.