It'd be nice if it was limited to places like 4chan. But as I always say, powerful people believe all the stupid things regular people believe, so no surprise investment funds act like that too.
Most of the incel, anime, doomed, and bro culture that was prevalent / nascent there 15-20 years ago is now super mainstream.
What it really is is the interface. It’s where things go when they are on their way out, like discarded scientific ideas, but it’s also where new things first appear.
If you watch the fringe you know what’s coming and going.
It can be hard to tell sometimes which it is though, coming or going.
It’s really hard to predict what becomes relevant - I would have never guessed that the “chad/stacy/virgin” archetypes are now so common place that even my grandma knows what it means.
Whereas other huge memes from back then like EFG never got popular.
Today I feel like a lot of it has retreated into closed groups, which makes it harder to keep an eye on it. Frustrating for someone who likes to watch it, but also might be a good thing since it might insulate it a little from the culture vultures.
Pre-Internet it was music-drug-party culture (those three always went together), which was full of weirdos that ended up setting trends. Gay culture was big too, especially when the latter was persecuted and kept at the fringe. For example a lot of techno, house, rave, and similar electronic music came out of gay black culture, which is a minority subculture among a minority. Hip hop came out of poor urban black culture, which developed turntablism and weird ways of "creatively misusing" cheap synths because they couldn't afford expensive ones. Blues came out of the poor South, mostly among blacks, and rock came out of that. Etc.
There's a very weird paradox at work here where persecution of a minority or a subculture empowers them and vice versa. I'm not saying persecution is good. Obviously it massively sucks to be on the receiving end of it. But it forces you into a liminal space that's more creative. By "persecution" I also mean just being viewed as incredibly weird or offensive and being soft-persecuted through ostracism and deplatforming. That applies to incels, oddball 4chan autists, etc., subcultures that definitely get either mocked or reviled by a lot of people for various reasons (some valid some not).
I think most of the sub cultures you mentioned are now firmly in the mainstream culture - it might just be my bubble/bias - but gay/black/furry/genderfluid/fandom/rave/techno culture is nowadays so prevalent that it doesn’t even register as something unusual.
To me that is a huge difference to 10-15 years+ ago and tumblr besides the chans is definitely one of the places that drove this change; also all the other significant social media’s of that era also had an influence of course. But the anonymity that 4chan provided was kind of unique and so the more extreme/unusual cultures gravitated there I think. Tumblr was special too for sure.
Nor did every thing 4chan invent catch on.