You see the answer to that every day on this site.
The difference is the vision of their respective members and supporters.
As a result, the ACLU operates strategically while the NRA operates tactically.
That is, the ACLU carefully selects its test cases. This can include selecting cases that will go before friendly judges. The ACLU often moves slowly and incrementally. Sometimes they won’t take a case simply to avoid the risk of a bad precedent if they lose.
And its members accept this approach.
OTOH, most NRA members (and non-member gun owners) would never accept that approach. They want instant gratification (and they want it now!!
). If the current NRA leadership won’t fight every battle every time, the NRA leaders stand a good chance of losing their jobs (and, upon occasion, they have).
They are expected to pick battles simply to fight them instead of to win them.