What's the meaning of "as it did" in this sentence?

Islamic law is the result of an examination, from a religious angle, of legal subject matter that was far from uniform, comprising as it did the various components of the laws of pre-Islamic Arabia and numerous legal elements taken over from the non-Arabnpeoples of the conquered territories.

Solution 1:

The common phrase "as it did" is another way of saying "as was the case"; it is a reinforcement of an assertion. It is somewhat redundant, but used for emphasis.

Consider these two sentences:

Victorian Britain was truly an empire, ruling as it did over huge portions of the entire world.

Victorian Britain was truly an empire, ruling over huge portions of the entire world.

As you can see, "as it did" adds little to the sentence. With no help from those three words, the reader understands perfectly well that the writer is claiming Britain ruled over much of the world during the Victorian era. All that the extra words add to the sentence are a rhythmic variation and a confident tone. To include them or not is a matter of style.

Solution 2:

comprising as it did is simply a stylistic variation on as [since, because] it comprised.