TOS was, for many years, the big deal in television SF. And while I would say fandom in general was always evolving as people were exposed to more SF and reflected back on TOS and Star Trek in general. That's still going on.
Looking back I think fandom stated to really change (or perhaps fracture is a better word) when TNG came along. TNG attracted not only some of TOS' fans, but also fans who were never into TOS as well as some who weren't into any SF at all except TNG. And each successive series and then the reboot films signaled another fracturing.
When it was just TOS (along with TAS and the first six films) as well as tie-in merchandise it was pretty well understood what it meant to be a Trek fan. But with each new series and then reboot it got ever more subdivided.
Add into that mix people's exposure to other SF and fans projecting some of that back onto Trek (or whichever version they prefer).
honestly, the 'Trek/Not Trek' type of divergence started with TAS - and then again, when TMP came out, there was a big "It really doesn't feel like Trek, the characters are 'off' and the Enterprise is too different, and the Bridge has TWO turbolifts'...etc.
To try and claim 'divergence' started with TNG (I did start a BIG divergence to be fair that I saw); is whitewashing what were pretty large divisions previously that happened with both TAS and the TOS feature film run.
ST II:TWoK did unify a lot of rfandom as many who only cared for TV TOS did see that TWoK did get the characters back more to their TV attitudes and portrayals.
Which is interesting because TWOK also created a riff between Meyer coming in as an outsider and establishing his own point of view on Trek that even GR disagreed with.
I was thinking about this a little bit more, and I think one aspect of fandom is a reflection of society. Fandom has shifted a little bit in terms of the accessibility of episodes, movies and the like being faster and able to instantly share your opinion. That has resulted in less appreciation of the production time needed to craft art (TV, music, movies, etc) and a greater inclination to want instant gratification.
It creates an odd reaction in society, that's for sure.
Didn't Paramount get death threats over leaked details from TWOK? Or am I mixing that up with what some of our loonier brethren did to poor Malcolm Mcdowell?
Actually there's a case where our little fandom has changed. Theres much less of the genuinely scary crap being directed towards the people making the show. We're faster to whine, but also faster to try and head off the stuff that crosses some serious lines.