God is so quiet

[possibletarian]

What you don't want to do is interchange the word 'universe' (a concrete contingent object) with 'exist' (a concept). They are not even synonyms. You can easily posit a possible world where something else besides our universe exists.

To ask why is there A and not B, we first both have to be sure that A and B are possibilities, we know that A (The universe) does exist, there is no, not universe to exist is there ?

Actually, we are NOT asking why there is A and not B. We are asking why is there A instead of not A. In other words "why is there a universe where there didn't have to be one?" 

We can imagine all kind of things not existing, but could the universe actually not exist, as to imaginary not exist ?
Could anything that exists actually not exist ? Sure i can imagine me not existing , but it wouldn't be the truth or any measure of reality.
We can imagine any number of things being different than they are, but simply, they are not, imagining a possibility does not make it so.

The reason he says it is meaningless as I understand it is because nothing is not a possible scenario.  It's a bit like asking why is that cloud not a non cloud.

When you say "nothing is not a possible scenario", okay, I don't think that nothing is a possible scenario either (for different reasons). However it seems you might be taking that sentence to mean that the universe must then exist necessarily, in which cae you are very much mistaken. Rickles makes it quite clear that concrete objects (and he mentions the universe as one of his examples) are all contingent entities--relying on something else for their existence. His answer is that the concept of existence must necessarily exist because you need it as a foundation to explain literally everything else. Concepts cannot cause anything. He never told us what he thought the cause of everything else was.

If we have already established that things exist, that's because you don't need to, do things that exist actually need a cause (as in creator)?. I think it's a clearer more honest question to ask what factors or circumstances came together to trigger the big bang. To imagine it otherwise is just that, imagination.