OP, are you just talking about this site or the community in general? Well I guess they're both one and the same.
I'd say the forum/community really peaked around 2017-18. Not just (the many iterations) of is, but the growing community all over the web. That one Discord server from those days was wild.
Many people talked and joked about the community having a shelf life at the time, and in a way, it did; mainly due to discussions quickly becoming par for the course. Doesn't mean it's particularly dead today - still a good community.
I'm an oldcel who first started out in the first wave of the PUA crap, eventually becoming disgruntled with that scene and finding places like PUAhate, exposing "gurus", etc. That place didn't start out as an incel sanctuary, it was a forum for disgruntled PUA students who would get no results, people who discovered they were scammed by frauding PUA "masters." Eventually the PUA discussions quickly ran it's course and more "off topic" discussions on relationships and females took over. TBH, at that point it was more of a MGTOW forum, in fact, there was even a bit of MGTOW crossover, not a lot of emphasis on lookism had taken over yet but the theories and ideas slowly started showing up. It wasn't until FACEandLMS dropped that first legendgary video on youtube around the year 2014... It all took off from there. Ironically, that was the same year St Elliot became famous. Weird coincidence.
That first wave of the incelosphere and IS was something to behold. You had to be there. That's when you had the countless, successful and funny Chadfishing experiments that were shared with gusto. Remember, this was at a time when foids were more naive to that, also at a time when these dating sites didn't have instant video sharing or whatever to verify the authenticity of the person, they just took fake Chad's word as the real deal. You also had the brave (perhaps idiotic) incels doing IRL catfishing and recording it for our pleasure.
Eventually the community began spreading into the public limelight. it was so surreal watching news broadcasts using buzzwords like "incel" and incel lingo like "blackpill." I remember when New York Magazine had "This is Chad" on the cover of the magazine, with a guy, post-op covered in bandages, the community went crazy. Someone even posted a thread "WE MADE IT ON THE COVER OF NY MAGAZINE!" lol! That's how excited people were that the movement was getting noticed and going somewhere.
Also around that time, you had journalist and people from networks trying to recruit people from the incel spaces to appear in Incel documentaries. The docs were made, you got to see some of the posters. People like FaceandLMS, who used to be very active on the forum(s) and the discord server, was completely against people signing off on those documentaries and interviews, but later, even he appeared in some interview/podcast lol.
IDK, it was amusing and very fun at the time. The freshness of it made it more appealing and you just wanted to soak more of it in. It was almost like if every day something new would come out - new studies/new breakthroughs, new scandals between members, etc... It was a very niche community where you had to be in the know to understand - Today, everyone knows. The lingo isn't exclusive to incels any longer