I can only recommend watching Innuendo Studios' _Alt-Right Playbook_ series for a deeper understanding of the dynamics, but if you don't have the time I'd at least recommend watching this one: https://www.youtube.com/watch?v=xMabpBvtXr4

All of 4chan, but especially /b/, is built around "haha just kidding ... unless", ridiculing people for getting offended while "trolling" with the most nefarious opinions and defending them "as a joke". This escalated with /pol/ which at some point became mask-off unironically white supremacist.

This is not just about 4chan being too white and too male and everybody self-identifying as NEET (whether as a joke or in earnest). The perpetual "ironic" regurgitation of racist, misogynist and anti-Semitic talking points attracted Nazis because it allowed them to hide in plain sight and they very successfully used it as part of their pipeline by getting people to repeat their jokes until they stopped laughing.