I have a bit of an ambiguous query, but, there are two things I have noticed about TOS fandom, let’s say in the 80s but prior to TNG coming out. I want to know if you noticed it, too, or agree, or have any sort of explanation.
1. Disproportionate love for Sulu, Uhura, and Chekov
There is a segment of fandom which always thought these characters got the shaft and should be as much featured as the big three. (I first noticed this in book reviews, which always gave points to authors who featured these characters.)
2. Disproportionate love for Klingons
There is a segment of fandom which seems to think they are as cool and important as our heroes in the Federation/Starfleet. (I first noticed this in gaming—often games would have you play as Klingons.)
Whence these puzzling phenomena? I wouldn’t say I don’t see ANY appeal in these elements, it just seems within TOS itself they are much more minor than they came to be perceived, if that makes sense.
In 1. you left out Scotty. The 'fab four' became more loved because they tended to do more Star Trek Conventions that Shatner, Nimoy and Kelly in the old days. It's also when the first stories of "Evil/Bad Shatner..." started making the rounds too. (Personally, I tought that was probably more due to they wanted interesting stories for their convention stage appearances. I have no doubt Shatner did things on set to make sure Kirk was the center of attention, but he WAS the lead/star of the show and in practically every scene in most scripts. Th other four were cast extras (much in the same vein of similar contemporary shows in the 60ies like "Voyage to the Bottom of the Sea" who also had recurring crew extras.)
My point? Shatener was probably on the set for a 5-6 days of filming a week, where most times any of those 4 were probably working 1 - 2 days at most a week, They're all actors, and ANY actor would love more to do - but again, the (at the start) two stars were:
William Shatner (Lead)
Leonard Nimoy (Co-Star)
and about half way through Season One
DeForrest Kelly (Co-Star)
The other 4 were window dressing, who after the show becaume more popular, made a living of going to conventionns and playing up their roles in the show.
I say 'playing up' because hey: does anyone hate "The Doomsday Machine" because Lt. Uhuar isn't the Comm officer on the Bridge for that episode? No. It's still one of the top TOS fan favorite episodes despite Nichelle Nichols not being in a single frame.
So, yeah, I thionk they became more loved by the fans because they (through conventions) cultivated a relationship with and did make money from fans (with autograph signings, etc.) by going to conventions regularly.
BOTH Shatner and Nimoy (and post Star Trek Nimoy with more visible success at first) tried to keep their actual acting film and TV careers going. Nimoy took a supporting role on Mission Impossible, while Shatner would do anything he could get from small documentaries to TV commercials and made for TV movies, etc.
As for the Klingons (and Romulans) - it doesn't matter if it's TOS or the TNG era. There were ALWAYS a small hardcore group of fandom who identified with and felt these species and characters got a bad/undeserved 'rap'; and were more interested in having stories about them and building out their respective cultures more.
I've been a fan since 1969 (at age 6) - started getting more directly invoved in fandom in the late 1970ies and early 1980ies when the feature films hit - and I would say what you dewscribe above was any more or less prevalent then it has been through the 90ies and early 2000's as it is today.
The only difference with the TNG era was that - from the start they decided to play up the "It's a ensemble cast..." aspect because they didn't have a bigger name star in the lead (Example - for TNG I'd say in many eyes Lavar Burton (from ROOTS) was a bigger name in the U.S. audiences eyes then say Patrick Stewart back in 1987. Same with all the Berman era series - the ensemble of small A to B list and genre actors was made the 'draw' - along with the fact that it was Star Trek <--- which was (and still in now) a draw for some folks regardless of who is cast.