Most historians now agree that the downfall of the Nixon administratio

Mention the letters against the options as well.

Most historians now agree that the downfall of the Nixon administration began with the 1971 release of the Pentagon Papers, not seeing them[/color] as an implication of the Nixon administration (they did not), but rather because their disclosure set in motion a series of paranoid actions that culminated in the Watergate break-in.

The major issue is lack of parallelism (not seeing them...., but rather because...). The elements need to parallel for not x , but rather y...

A) seeing them as an implication of the Nixon administration (they did not), but rather because their disclosure set
Incorrect. As stated above.

B) seeing them to implicate the Nixon administration (they did not), but rather setting
Incorrect, awkward construction.

C) seeing them implicating the Nixon administration (they did not), but rather, disclosed, they set
Incorrect. As stated above (lack of parallelism)

D) because they implicated the Nixon administration (they did not), but rather because their disclosure set
Correct.

E) because of the implications they made about the Nixon administration (they did not), but for their disclosure setting
Incorrect. "but for their disclosure" is awkward