You can add the word "porn" to the end of almost anything, which means that you achieve delight from viewing such a thing.
But when a couple who is breaking up are yelling and swearing, and throwing toasters at each other, drawing a knives and he rips out her weave, and you start to get smug and laugh at their tragedy... That's divorceporn.
It's when something regular metamorphoses into garish entertainment.
There was an Ally McBeal about group marriage. One of the arguments against group marriage was that a cunning business person could marry a thousand people, claim them all as dependants and defraud the Inland Revenue Service of untold millions of dollars semilegally.
I saw on 60 minutes this guy in Oz with 9 "wives" and dozens of children who collects 30 grand in social security every week... At least those were the numbers I heard a few year back... Point was he lived in a tent and the wives ran the show.