My view is only one viewpoint, and it is like a little painting I’m working on as I progress through life. I’ve shown a part of it to you, and it has some elements that may be imperfect. I think no matter what I do, there will always be those axioms and initial conditions which you (or I, or anyone) can question. When will the painting be finished? When it is perfect, or when it is beautiful? It may never be finished by me or anyone in this life. But we’re working on it. I think that’s saying something for us and life in general.
You’re ambitious, which is great. You’re respectful, even greater. I do, however, believe it is beyond my individual right and ability to attempt to provide an explanation for God, such as the causality of God’s existence. I do not know if such a thing can even be known, at least in the sense you seem to seek.
I feel God in my life, as real as the sun, grass, and breeze, but this feeling is always just beyond my complete and total understanding.
Honestly, I think love is the answer. I also think more will be revealed, my friend.
I view the will of God as the “why” and the physical laws of nature as the “how”. When people say “everything is connected” I interpret that to mean while it’s true that physical causes and effects behave according to natural law, the will for a desired outcome is provided by a higher intelligence.
To answer your question, the universe exists because God wills it to exist.
While we’re on the subject, many believe in a hierarchy of supernatural intelligences (e.g. angels and demons). A scientific explanation for this hierarchy may be living beings that occupy dimensions other than our own (e.g. “higher” dimensions that operate on “lower” dimensions).
See, e.g., https://m.phys.org/news/2014-12-universe-dimensions.html