What was the purpose of kidnapping the young people in Ad-vitam

Warning: this question contains spoilers for the French TV series Ad-vitam.

TLDR: what was the purpose of the "experiments" on the young people at the end of the series?

When the bodies of the youths were found in the beginning of the series, the working assumption of the detective was that it was a suicide pact.

However, during the investigation it was revealed that they were actually part of a larger group of young people who were abducted under pretence. The kids who were immune to regeneration were killed straight away, and these were the bodies that sparked the investigation. A larger group of kids were then found to be used in some bizarre experiment by a secret wealthy society, where it seemed that they were being subjected to some kind of reverse regeneration process where they were forced to age rapidly until death. The society onlookers seemed excited at the start of the experiment but it seemed that, as the kid got older and dies, they became disappointed, as if they expected a different outcome.

My question is: what was this experiment and what was the "hopeful" outcome for the onlookers? As far as I could tell, this was never explained in the series, but it may have been alluded to and I missed it.

I found a thread on reddit where a poster stated the society were simply haters of young people and enjoyed torturing them to death. But that seems insufficient, because if so then

• why were the immune victims separated and killed swiftly? Why not torture them too?
• the members were clearly disappointed when the victim died in the experiment, as if they were hoping for a different outcome. I suppose they could be disappointed simply because "the fun is over" but given there were many more victims available, it seems odd.
• why the elaborate mechanism of subjecting the victims to a reverse regeneration, there are after all many ways to torture people.
• Just my opinion, but I find the "device" of a big an influential society, comprising of some of the most upstanding people in the country, with such a sadistic and depraved purpose, to be a disappointing explanation for the events of the series.