but isn't the problem that you could get stuck in an infinite contingency loop? i.e if you pick God, what if God is contingent and so on. Sure you can say something is required but it's rather arbitrary.
It's only arbitrary if there aren't good reasons.
Dozens of reasons have been given in philosophy, it's up to you to decide if any of them work.
One of the big differences would be to point out that the universe is completely composite, whereas a foundation could be purely simple.
Josh Rasmussen is a great communicator about this!
https://www.youtube.com/watch?v=TX79xXgi44o&ab_channel=TheUn...
I can understand why you would like the question of why God is necessary to be "misplaced" (which is a euphemism for what, exactly? It is no less coherent than the other questions being entertained here), but, with your 'that's it", you are simply refusing to look further than the answer you wanted.
Furthermore, as I am sure you are aware, 'God' is a loaded term, on which has been heaped a huge amount of conceptual baggage. Therefore, I assume you chose to write 'God', rather than some more neutral term such as 'necessary cause', for some purpose - but what? Your argument for there being a necessary cause would not offer any reason to justify any of that baggage.
The cool part about this definition of God, is that it necessitates the existence by definition, and gives a falsifiable hypothesis.
Continuing with this definition, current cosmological theories would then imply that the Big Bang is God. Though this explanation of the beginning of everything leaves me unsatisfied. It just feels like something else kicked everything off.
We really need a way to peer behind the Event Horizon of the Big Bang, which we obviously can't do empirically, so we are stuck using logical deductions.
I personally think studying pure math and some of the more untested physics theories like String Theory, and Stephen Wolfram's physics project give a lot of food for thought.
Enumerating every possible pattern, while computationally infeasible, still paints an interesting landscape, even granting how little of it we can describe.
You say we are stuck with logical deductions, but the thing about them is that they are no more true than are their premises, so analytical metaphysics grounds out in a personal and subjective choice of axioms (subjective in the sense that no-one else is logically compelled to accept them.)
Assuming God = Beginning of the causal chain, Finding this prime mover becomes a tangible physical hypothesis.
I don't think most religious people would agree with this definition of God though.
Also, if the information needed to confirm the beginning of the causal chain is locked behind an Event Horizon, then I don't know what to conclude about this.
I think it's possible to build a model in our slice of the universe that can let us peer beyond such limitations. But I can't be sure.
Rather ironically, the "there must be a prime mover" argument for God can only avoid being blatantly arbitrary, tendentious and self-serving by saying God had no choice in anything, which is definitely not what most religious people want to believe.
To rephrase what you are saying for my own brain: An original causal event may still have dependencies that aren't necessarily bound to it in time or space. And these dependencies may have their own structure that are suspectable to infinite regress.
Perhaps an example of this is how all the fundamental constants have very specific values that are required aprori for anything to happen in the first place.