Hey — So I just tried the Q are here are my thoughts —
– I think the most important issue (and I could be misreading your thought process) is that you may be confusing necessary and important (or vital) — the test writers view these as being two very different concepts, and they will continuously test whether you can differentiate between the two — keeping those distinct in your head can make a lot of tempting wrong answers less tempting (as well as, obviously, helping you out more directly on necessary assumption q’s and such) —
On the LSAT, necessary means absolutely required. I agree with you that his case strategies were vital, but we have no proof that he absolutely “had to use them,” which is what we would need in order to justify (D).
“Inferred from the passage” does not mean the right answer has to represent the passage as a whole. Used in this manner, the statement can also refer to something that can be inferred from a very specific part of the passage.
A couple of lines I saw that can be used for justifying (C) — “developed innovations” in the middle of the first P, and “originally considered to be a radical departure from accepted conventions” at the end of the final P —
Hope that helps, and if you have any follow up just let me know — Mike