Since experiments carried out by different people in different locations tend to get the same result, the evidence is that there is a consistent underpinning to the operation of nature. Technology designed on this assumption works reliably. There had been no repeatable and reliable observation to give even a hint that it is not true, so it is a near universal assumption that people who operate in the world make.
Where does "nature" begin and end? How does it's parameters relate to "existence"? If we can conceive of the term 'nature', doesn't that imply that the conceptual realm extends beyond the natural realm in some way?
Physics is the study of this underpinning.
Yes, I know. But there seems to be quite a bit more to existence than just the physical realm. And if the conceptual realm transcends it in depth, scope, and import, as it apparently does, then what do the limits of physics really tell us about anything but the limits of physics?
Why does your question matter?
If the underpinning includes an origin, then it is physics that will be the method that will uncover it.
You're getting bizarrely abstract, here. What are these "underpinnings of physics"? Aren't they just the source and limitations of energy? And as yet, we have no idea what the origin of those are. Yet the fact that we can ask the question at all implies that there is a realm of existence that transcends and expands beyond the physical: the conceptual realm. So if we are going to contemplate the origin of existence, we're going to also have to include the origin of transcendency, not just of the physics, itself.
So the mystery increases.
The variability of personal experience is the weakness of art in determining anything in general, and in philosophy in determining anything useful in this area of learning.
Or perhaps this need for consistency is the fundamental weakness of logic and reason (based on fear for survival), that art transcends through intuition, spontaneity, and faith. Perhaps the individual experience can go where the general consensus can't.