In the multiple women scenario the women fight over who has to be the cleaning lady and do all the bitch work around the house. It can work if the dude is alpha enough to keep maintain control of the household.

It's the multiple men scenario that's never stable. The woman treats the men like her children and there are constant cuck fights. The dudes often murder each other or any children that result from the arrangement. It's just not a workable relationship structure even ignoring the fact there's nothing in it for the men besides sloppy fourths when and if she feels like it.