It just happened. I'll explain, but first:
Want to know why this shit is so prevalent of /gif/?
People will call you a conspiracy theorist if you call out the amount of threads focused or when black stuff leaks into other threads, but it's usually incredibly intentional. Whether it's shill groups (People in discord, skype, etcetra) coordinating shit on /pol/ or just a few people with the same content to post every thread.
On /pol/ it's incredibly easy to recognize due to flags, IDs, and posting styles.
Unfortunately on other boards, like this if there's any attempt of concern trolling, shilling, samefaggotry it is hidden behind anonymous posts which can create an illusion of a group of people being against you while it's very usually one or two people in a thread of 75 posters. So, for blackedposters it basically enforces their rhetoric and makes people who are ignorant to troll patterns easily moldable and that's usually where fetishes can be adopted... especially if you're a young easily influenced anon from 16 to 22
It doesn't help that media, music and even government organizations enforce this belief of the "Insecure, angry, disgusting white man" which just enables the fetish further and creates a fuck ton of disenfranchised young men who unfortunately eat up this shit. However (I think white nationalist groups have realized it and may be in or the blacked posting aswell) it drives that disenfranchised white man to become a hate mongerer and likely develop mental issues and basically create further racial division.
And for the sake of saying it, there's definitely impartial people who enjoy this stuff. But considering the constant bait efforts and just the multitude of these threads with the same format which even leaks onto /pol/ the people who aren't pulling bullshit seem to be a minority if not it makes an implication they do not exist at all.