.... or this scenario:

When the Spanish flu decimated millions in 1918, one of things researchers learned was the major portion of those killed were not the elderly or young children, as one would suppose, but the healthiest and strongest of immune systems. It created in the body's immune system a cytokine storm of anti bodies. Without going into detail it means that the body, in reaction to the virus, created a feedback loop which overwhelmed itself. The stronger the immune system the quicker you died.

Now many assume that the Spanish Flu virus was wiped out, or rather burnt itself out, resulting in no more infections and transmissions to people - no more flu. Ergo no more viable samples to tinker with up at Fort Detrick or other Bio-Labs. However, one clever person realized that many native Inuits up near the arctic were also infected and died. They were buried, but buried in the permafrost. He thought that there just might be viable samples in stasis just waiting to be thawed out and tinkered with. He was right. They went a up there, dug them up and found viable samples.

Now let's suppose they did a little gene splicing and created a new Spanish Flu. One far more lethal, but one that would only attack those who had their auto-immune systems hot wired and ready to create a cytokine storm. Sort of a precursor if you will. A precursor touted as a flu vaccine. Not long ago I remember reading of meetings where this was planned. And, as no one really wanted to pick and choose who would die, who wouldn't, they created a virus that would choose for them. Only they needed that precursor shot first. Ergo some got the real precursor in their vaccine shots and some received the prophylactic. It would all be mixed up so that nobody knew which shots, or vaccines, had it, and which ones didn't. That way no one could be held accountable for choosing and everyone involved could have a sort of clear conscience.

Global culling of clueless sardines.

Very risky strategy.  The rich also avoided the Black Death by escaping to unpopulated estates in the country but the net result was that they lost a lot of control of their serfs and feudalism was hamstrung in Europe.

I think if the oligarchy was this powerful and organised we would be dead already.  Kill even 10 percent of the world's population and the secondary and tertiary effects would be powerful and unpredictable as history demonstrates.

Population will start declining within a few more decades anyway as more and more third worlders use contraceptives.  Why would the super rich care?  They have their own islands, private estates, helicopters, private jets.