Non-philosopher here, though I enjoy reading about it. Without getting into complex deductive arguments, suppose I say the following: Define the entities of the material world however one likes (maybe at bottom, to keep it simple: energy and forces of nature). Considered in it's entirety, it seems fair to inquire about the "cause" (define cause however you like) of this category of stuff, taken as a whole.
Now, to me it seems nonsensical to posit that something within this category is the cause of this category itself. More precisely, even if we have an infinite series of causal relations, possibly a loop, I would maintain that it's fair to ask "Why this particular series of causal relations and not another", and so even if each part of the series is accounted for, I would still maintain that a regress is an unsatisfactory answer.
It therefore seems that all one is left with is a "brute fact" argument. Maybe the series of causal relations is simply a necessary fact, or one which literally has no explanation. But physical states of the universe don't seem to be necessary, and one may be comfortable with countering a "brute fact" with a "brute rejection": it's quite unsatisfactory intellectually.
What is one left with? To me, it seems that some entity which "transcends" the property of physical existence would be the most parsimonious solution.
Again, I made no real deductive argument, and am just trying to understand the options, and what one is left to force to believe if we reject this or that premise.