If every effect doesn't need a cause, then yes the argument fails. Anyone can conjecture about pre-universe universe, but there's no reason to assume effects and cause don't apply to it
Actually, there is very good reason to assume causality as we know it doesn't apply in that context.
For starters it requires temporal conditions to exist. And at T = 0, such conditions do not exist because the universe doesn't exist. And temporal conditions are an inherent part of the universe.
It's like asking "where did the universe start?". The answer is "nowhere" - and even that isn't actually correct.
The problem is that any
place you can point to, is a point IN the universe. The universe didn't start IN the universe. See?
Our minds have difficulty comprehending nature in a context where neither space or time exists. So it feels counter-intuitive. That's the case for pretty much all of physics that deals with conditions that are not actively part of our perception. Relativity, quantum mechanics, etc. It all feels spooky and weird.
But it is what it is.
To say it was eternal and changed into a cause and effect material universe by itself with no cause, doesn't stand to reason.
It doesn't stand to your
intuition.
Whether or not in stands to
reason, depends the actual physics theory/hypothesis that deals with the origins of the big bang, the evidence in support of it and how and if it can be tested.
Even if we can't be certain cause and effect always applied to it, God is infinitely more likely
How are unproven, unfalsifiable magical beings that have NO precedents whatsoever and which are literally indistinguishable from things that don't exist, "likely" in any way?
"Likely", how? Why? Because you already believe it?
then that universe existing in a state with no cause and effect application of rules to it and then having cause and effect rules applied to it all of a sudden with no cause.
Your biggest mistake is assuming that the physics
of the universe also apply when the universe doesn't even exist yet.
This makes no sense.