1. That they were published with obviously impossible results (inspecting the genitals of 10,000 dogs while asking owners about their sexuality).
2. It's where they were published. e.g. In the #1 "best" feminist journal Hypatia.
3. It's the evil in the messages they got published. They got a 3000-word except of Mein Kampf published, by rewording it in the language of intersectional theory. They got published recommending that "privileged" students be physically chained and silenced during class. They got published by proposing men be trained like animals. (This is not the same as learning about human behavior by studying dogs; it is to suggest that it's okay to treat people like dogs if they're born a certain way).
All this demonstrates a field of study that is not just soft in terms of intellectual rigor ("implausible"), but is willing to casually support reprehensible policy ideas if they're framed within a specific neo-Marxist belief system and targeted at men or white people.
Bear in mind that many of the people producing the papers in these fields receive public funds at public institutions. They project an image of being neutral scholars to justify those funds. What this hoax has done is given evidence that they are not neutral scholars. They are moralizers, activists, revolutionaries working to target a specific group of people, and are not very concerned about the rigor of the intellectual pathways they use to get there.
A group of people dedicated to a process are called scientists. A group of people dedicated to a conclusion is called a religion or an ideology. Social scientists claim to be the former. But the hoax papers demonstrated that, at least with some regularity and even in the highest journals, the social sciences act like the latter.