Hm I kinda doubt that stupidity is the only reason for this PR disaster. One does not simply stumble across a random website and does a AMA on it without some basic research. I would guess someone at THQ Nordic who was involved in the whole process knew exactly what 8chan is.
Especially considering that 8chan isn't even accessible through google.
That's the hilarious thing: How can supporters go along with the narrative as if THQ was an old man who got lost in an alleyway, when you can't even access the site through normal means?
Seems pretty obvious that either one of the higher ups like 8chan, or they expected this and wanted to be edgy and cause controversy to spread their name.