I think it shows how ingrained in society mono is that the poly person is the one being vilified here. I see the chaos as a result of the incompatibility, if that makes sense.
Also the poly person wrote a popular book about it using his version of the narrative. And the poly person is held up as someone who is good at these relationships and is an expert.
His ex's didn't have anywhere near the platform he had. And they had to watch as he told their stories (in ways they didn't agree with) to explain his emotional arch.
Also Amber and Eve are poly. I don't think it's as simple as we all want to pick on the poly person and not look at the choice of mono people who choose to stay with poly people.