The NRA's cowering "endorsement" of Bob Dole in 1996 wasn't 30-40 years ago, and IMHO had a lot to do with the passage of the Lautenberg Abomination.
Did the NRA endorse Dole or not? What's that have to do with the Launtenberg Bill?
You're going to have to ask yourself the question, if those other gun groups are so important and powerful, Why didn't they stop the bill?