Please, review my paraphrase and tell me what is wrong

Question

So startling would his results appear to the uninitiated that until they learned the processes by which he had arrived at them they might well consider him as a necromancer.

This is the original phrase

that until they learned the processes by which he had arrived at them

This part is particularly confusing to me .

Before they(those uninitiated) learned the method which he obtained, his results would be so surprising to those who don't know anything about them. After learning, they will think of him weird.

And I tried constructing a paraphrase. I'll give you additional information about this, in case the context is not clear.

Its somewhat ambitious title was “The Book of Life,” and it attempted to show how much an observant man might learn by an accurate and systematic examination of all that came in his way. It struck me as being a remarkable mixture of shrewdness and of absurdity. The reasoning was close and intense, but the deductions appeared to me to be far fetched and exaggerated. The writer claimed by a momentary expression, a twitch of a muscle or a glance of an eye, to fathom a man’s inmost thoughts. Deceit, according to him, was an impossibility in the case of one trained to observation and analysis. His conclusions were as infallible as so many propositions of Euclid. So startling would his results appear to the uninitiated that until they learned the processes by which he had arrived at them they might well consider him as a necromancer.

Source: A Study in Scarlet, Arthur Conan Doyle

Answer 1

So startling would his results appear to the uninitiated that until they learned the processes by which he had arrived at them they might well consider him as a necromancer.

We see inversion in the first clause to emphasize startling; let's rearrange in normal order:

His results would appear so startling to the unitiated...

And now for the that-clause, which is interrupted by an until-clause:

...that {until-clause} they might well consider him a necromancer

They would only think this

until they learned the processes by which he had arrived at them [his results]

P.S. At the heart of this sentence is a so {modifier} that pattern.

The tea was so hot that we could not drink it until it cooled.

The gardener's fence was so low that even a fawn could leap over it to eat his vegetables.

We can invert the word order to emphasize the modifier:

So hot was the tea that we could not drink it until it cooled.

And we can nest the until-clause inside the that-clause

So hot was the tea that, until it cooled, we could not drink it.

Answer 2

So startling would his results appear to the uninitiated that until they learned the processes by which he had arrived at them they might well consider him as a necromancer.

does the following help?

People who did not understand what he was doing might think that the reason that he was able to produce such surprising results was that he was a magician (or a wizard).

the uninitiated -- this means: people who have not learned something (or have not been introduced to something)

the processes by which he had arrived at them (the results) -- this means: the methods he had used to produce the results

People observing him producing such surprising results would think that he must be using magic, until they began to understand the methods he was using.