If it was always required then the positive explanations would require positive explanations themselves.
Example:
Capitalism is better than socialism because of the economic calculation problem → Socialism has the ECP because it lacks a price system → a capitalist price system doesn’t have the ECP because it gives people a way to signal how much they value various products compared to each other → which is necessary because there is no intrinsic value, rather only “subjective” value exists → … → humans act → … → existence exists.
I had something like this in mind. But this gives the sense that the chain is really long, and the problem is that it would be cumbersome, which wasn’t my idea. The idea was more that between each arrow you could always make a closer connection. But now that I’m looking at it, it seems like you can’t always go closer. Like in:
Capitalism is better than socialism because of the economic calculation problem → Socialism has the ECP because it lacks a price system → a capitalist price system doesn’t have the ECP because it gives people a way to signal how much they value various products compared to each other
I see how in an explanation you could cut out the second sentence here. But I can’t think of something which would be necessarily closer than 1 → 2, well maybe other than explaining what the ECP is, and then what calculation is, and what a problem is, and so on. But that isn’t necessarily infinite, you could make long chains but you only have to go through explaining each of the concepts in the claims. And even though that expands into really wide and deep trees, the trees would eventually start tightening and reducing towards “existence exists”.
And that is fine because “existence exists” does actually serve well as an explanatory foundation, i.e., the concept you would always reach if you went on explaining every explanation. That is different than serving as a justificationist foundation because your idea of “existence exists” could be misunderstood. But I think you can reach a foundational explanation, which is not the same as explaining everything as in making you understand everything, but rather that it is implicit in everything.