The fact of existence being, just illustrates that existence is.
Quite true! There is no reason to assume this isn't what the biblical authors are pointing out either. In fact, they point out not just that existence is a fact, but that it is "one". It is unified; a unified whole. Being is an existential fact. It's self evident. So why point that out? Because people tend to think it isn't for some idiotic reason.
It doesn't speak to the WHO or WHAT behind it at all.
There is no "what" behind it. Things come into existence. Things cease to exist. Existence is eternal. As far as "who" is concerned, it isn't about identification at all, but simply to point out that there is all the difference in the world between subjective knowing, and those things that are objectively known.
It says nothing about there being a God, many gods, or no gods.
It points out a self evident fact, i.e. that life doesn't just spontaneously come into existence through haphazard undirected chance. That's a scientific fact. There's no good reason to assume that as a possibility.
We need revelation for the details of the WHO or WHAT to be made known.
Who cannot be known. Only things can be objectively known, and "God" doesn't objectively exist.
Why not SOME INDIVIDUALS or SOMETHING, or even SOMETHINGS?
Because things come into existence, and cease to exist. Separate individuals are an oxymoron. They are literally contradictions.
Without revelation one would not know that existence wasn't the result of the accidental undertakings of a pantheon of powerful entities,
Simple reasoning can point out that isn't the case.
a single powerful entity,
Again, to reduce God to a defined entity is asinine. We haven't escaped our own anthropocentric ideas.
or a power source that has no will or persona.
A power source? We can deduce that there must be a source or origin to existence. We can call that source "God" with no fear or being refuted simply because it's nothing more than a convenience to facilitate or expedite discussion. That's what words are for. Ironically when it comes to "God", the gospel writer points out that there is only "the word".