What's the difference between 8chan and 4chan? I don't really pay attention...
8chan was created in 2013 as a result of dissatisfaction with imageboard moderation. Theoretically, it was designed to prevent poor moderation by allowing people to create their own boards and move the users onward. In practice it was just a lot like Reddit, where people would make boards to enforce their bizarre moderation standards and personal biases on.
Around mid 2015 it got the notice of neo-nazi types who proceeded to organize attempts to take over boards. They'd spam boards until their owners abandoned them, then claim them. Downtime, far right subreddits moving into 8chan, and server issues made pretty much everyone but them and very dedicated users leave by the end of the year. After claiming enough boards, they organized raids on Voat to try to turn it into a neo nazi hugbox, too, which functionally killed that site's community.
Eventually the original host and owner left as a result, because the site had become a collection of neo-nazi echo chambers. He no longer had enough power in the site to actually shut it down, because a lot of technical issues and attacks on the site lead to a man from 2chan purchasing the site and providing server access. This gave him functionally full control over the site. The old owner has repeatedly asked the new owner to shut the site down, since, because he views it as just a mouthpiece for neo-nazis and not a place of free speech. Obviously that has done nothing.
I dunno what happened after that because I stopped using the site around mid 2016. I do not think this will be much of a dent, either, because the site has suffered through way worse from rival imageboard communities and yet survived. Even if it stagnates the nazi types are too dedicated to leave and will continue donating to keep the site drawing a profit.