What is the plan here?
I'm not sure I understand the plan here. This isn't a ransomware attack, so the NRA's computer infrastructure is still functioning.
Generally, the threat to release documents implies that there is something in the documents that may be illegal or shameful. The NRA's legal woes have been documented, and there are multiple attorneys general from various states looking at the NRA's finances. Perhaps there is something in the stash that would help the case against the organization, but it seems that the organization has already provided plenty of evidence against itself.
If the plan is to shame the NRA, I fear that the hackers have betrayed their lack of knowledge of the subject. The NRA is the organization that, after each massacre of schoolchildren in the US, mounts a massive press blitz to explain why it is so important that we sacrifice said schoolchildren so that any idiot can assuage his penile inadequacy by owning as many guns as some small countries. The NRA as an organization has no sense of shame.