The NRA has been waning for a long time. Their member count is only so high be cause for a lot of the big gun shows, it’s free if you’re NRA. And an annual membership is sold onsite and costs less than one time entrance fee.
Their money is largely coming from large donations more to get republicans elected than anything about guns.
The inflated membership numbers is just smoke so they can maintain an air of legitimacy.
Lots of older people act like the “takeover” in the 70s never happened. Before that the NRA was mostly about hunting and argued against CCW. It’s actually pretty interesting how it all went down, and something relatively minor changed American politics for generations.