This was observed by me, not lived by me:
20 something years ago, some Germans showed up on a small village in the mountains. They started buying the empty houses. At that time, only 5 people were living in that village. All above 70 years old. One by one they sold them their houses too and moved to family or retirement homes.
When the village become empty, those Germans owned the whole aprox. 50 houses, and the lands and forests around. They asked and got, electricity taken there and started the process of re-building or modernizing those homes.
They were careful to keep the style and materials used in the area, most of it made by hand with locally sourced materials and techniques. The exception was the addition of bathrooms and several very deep wells that provided water to all the houses.
The construction took them over 2 years. Then they disappeared.
Months later the nearest village started to see young women with backpacks or bicycles on the roads leading there.
Police was called. They found a thriving community there. 1 man. Over 30 women. No cult. Just a VERY large communal marriage. All or most of the women have had children by now.
I visited the village a few years ago, they all now speak the country language. Kids go to school. No one has any problem with them.
They don't talk about their system, it's no one's business.
So, while I can understand that it isn't a common thing, I am absolutely certain that there are more cases of this all over the world. Maybe even under everyone's noses.
Will this work for everyone? I have no idea. Probably not.
There's a chance that something like this works for some? Absolutely YES.
Don't put everyone in the same bag. What may seem abnormal to you, may very well be the bread and butter of someone, somewhere.
Polyamory, even in extreme numbers, is REAL. Whether that agrees with you and your view of the world, or not.
Peace