You are unwinding past the brain that does the unwinding.

A rational agent goes "golly, I seem to implement Occam's Razor, and looking at that principle with my current implementation of Occam's Razor, it seems like it is a simple hypothesis describing that hypotheses should be simple because the universe is simple."

That is literally all you can do. If you implement anti-occamian priors the above goes something like: "It seems like a stochastic hypothesis describing that hypotheses should all differ and be complicated because the universe is complicated and stochastic."

So, you cannot 'run this logic down to the deepest level' because at the deepest level there is nothing to argue with.