Why do you find it difficult to believe the two are in near perfect alignment?
OK, it was a bit complicated when there were large stocks of military surplus still to be liquidated, the NRA supported both the GCA of '68 but also the later relaxation of imports of military surplus. On the other hand, do you really think the members of the NRA find it damning that one of the Nominating Committee members is "a timber company executive in Alabama" like Mother Jones does??? You think we're a hot bed of hatred towards free enterprise?
Very curious that the NRA put George Kollitides on the Nominating Committee because of his history, but it's hardly out of whack to have one manufacturer and one dealer member each; in fact, that sounds about right.
Your claim that it having 2 out of 9 members from the industry means they "dominate" the NRA leadership does not stand up to examination. Heck, even the Atlantic article you cite says "the corporate-front theory is still probably too simplistic" and "It's very hard to disentagle the interests of the gun industry from the views of gun rights purists."
Indeed: no gun or ammo manufactures rather obviously means no guns and ammo for us to shoot. We've very interested in their health, we're in the same boat, attack them, you attack us. And the NSSF does quite a bit for gun owners in a whole range of areas including the political, although their focus is of course on the industry.
As for "sole purpose", I didn't bother to read the cited article, but do you mean the NRA's gun safety efforts, largely credited with decreasing the absolute number of fatal gun accidents by 1/4 at the same time the population and number of guns owned has increased by 1/2, was solely done to protect "corporate profit"? Sorry, I'm not that cynical.