You and the poster you are replying to have totally missed the boat.
When considering intelligence agencies, its not the methods used to penetrate that are predictable. What is predictable is that penetration will happen and that it will be maintained covertly for as long as possible, and that nothing that will reveal the intrusion will be perpetrated on purpose but the intelligence gathering agency.
So the question of whether or not these American resources were hacked is immaterial. They were, and long ago. Consider them to be pwnt, and that they have been for years. Quietly and surely, intelligence agencies from all over the world have been sticking their sticky fingers into our government official's emails. Like, DUH! What do you think they have these agencies for? And if some stupid spearphishing attack worked, how much easier was it for the Russian intelligence agencies to get in with their studied and practiced wiles?
What they do not do, because it would be stupid beyond measure and completely counterproductive to the aims and goals of intelligence gathering, is broadcast all over the place the information they have compromised. This would let the hackee know they have been owned. Which would be just about the stupidest thing an intelligence gathering agency could do, short of taking a rusty antique hand drill and making holes in their own genitalia
The question is not "did Russia hack us?" The question is "Since rational and intelligent people know Russia has already hacked these people (and many more) years and years ago, and has had constant access the whole time, and since they wouldn't want to compromise their access to this information, who also gained access and subsequently revealed that access by leaking the documents?"