What was the deal with all that drama? I dipped out of here for pretty much from the second half of 2016 right up until the first half of 2018. I heard Tagaziel left and there was some minor drama over it, I see these days he posts a lot on Reddit making lore stuff and justifications for Bethesda Fallout and shittalking NMA whenever it comes up.
He and Sander abused their admin rights, basically (well, Sander did IIRC, Tagaziel was just...there. But he did agree with Sander in general, and they supported each other in various discussions). Few people got banned, some of which didn't deserve it at all, and they were banned because they expressed opinions different than those two - some of them did it in rude manner, some were respectful, but there were innocent casualties.
The whole drama was because of Gamergate/political correctness/what not at the time, of course. The two represented what you would popularly call SJW part of the spectrum, though to be honest, I've forgotten the details because most of it was inane crap. Strings of endless discussions and diatribes between opposing views that ended sadly and (if you ask me) unprofessionally, since these are admins we are talking about.
This alienated parts of NMA and some of people called them out on their bullshit behavior, from NMA newbies to oldies and Orderites. These two left (though they didn't lose their admin positions for all I know) and didn't come back since, at least not for any significant length of time. Banned people stayed banned. From what I know, some of them, like Akratus, moved on to RPG Codex. There was badmouthing of NMA here and there, people got upset yadda yadda yadda
All in all, it was pretty hectic and ugly. At least two users I recall didn't deserve getting banned were banned simply because they offered different opinions. Some of them tried to get banned tho, out of spite or whatever. Like I've said, ugly and unnecessary, but then again, it was just part of the wider trend throughout the web post-Gamergate with communities getting divided. Unfortunately, NMA got sucked into that too.
In any case, that is part of the past and valcik is blowing it out of proportions. "Big chunk of older userbase" didn't leave because of Sander or Tagaziel's shenanigans or whatever, nor has NMA turned into shit. I don't think anybody left because of that specific event, actually, aside from Sander and Tagaziel. I could be wrong, but them and banned people aside, nobody else cared that much to leave.
(Though to be fair, that overall period was kinda tumultuous with endless political shitposting which caused many people to leave, come back, leave again, get banned for justified reasons and so on and so forth. But that was a wider picture that lasted for years - the specific Sander/Tagz controversy was much, much shorter, but was quite poignant, so it stuck and kinda painted the whole period, despite generally being only a smaller element of a wider issue).
As you yourself say, it was minor drama all in all. If it didn't have political connotation to it, it would've been forgotten by now.
And yeah, Tagaziel is apparently an Bethesda apologist or something now, and from what I've heard, he badmouths this place on an occasion. As if being a furry wasn't bad enough. It's sad, really. He was a pretty cool guy before all that politics bullshit, and was a walking encyclopedia of Fallout lore, and was massively critical of Bethesda and bullshit in the series in general. There were awesome analyses of his on The Vault, dealing with various aspects of the lore and setting. But that was way back when, and I guess those have been deleted or forgotten by now.