The voluminous personal papers of Thomas Alva Edison reveal that his inventions typically sprang to life not in a flash of inspiration but evolved slowly from previous works.
(A) sprang to life not in a flash of inspiration but evolved slowly
(B) sprang to life not in a flash of inspiration but were slowly evolved
(C) did not spring to life in a flash of inspiration but evolved slowly
(D) did not spring to life in a flash of inspiration but had slowly evolved
(E) did not spring to life in a flash of inspiration but they were slowly evolved.

Answer is C

My Question:

According to the answer guide, the reason C is the right answer b/c "spring" is parallel to "evolved." "Spring" is in the infinitive and "evolved" is in the past tense, so why can it be in parallel? I understand in the idiomatic structure, Not X...But...Y, X and Y must be parallel. So...two elements can be parallel even if they are in different tenses?

My second question is "had slowly evolved" in D. I guess logically "had slowly evolved" makes sense here (Since the inventions evolve from a much earlier time period to an earlier time period), but is the reason it is wrong here b/c we need to preserve the parallelism of Not..X...But Y?

Thanks!