There is no “cartel”. Certainly not one that has maintained itself for 100 years. Way too much in the world is both revolutionary (mainly technology), thus prone to constant overthrow, and contingent. People push up constantly and displace the old chieftains, and they bring with them new interests. The new big guys want different things than the old big guys.
There is constant churn of elites, if one means actual individual people and their families. One needs actual persons to collude in secret after all. The Rockefellers, say, matter way less, relatively, than they did in 1970. Whatever golf course it is where things are decided, it’s not a Rockefeller on the green. Heck, I doubt much of importance happens on golf courses anymore.
If one means a general social caste, then you are on firmer ground, though here you have to depart from conspiracy theories, into sociology, as you are now dealing with millions of people. Go have a look at Angelo Codevilla.
At some Pont in the next year or so you are in for a terrible shock. Even JFK knew that we were all being ruled by a cabal of Central Bankers.