I have given this question thought. It is a little part of an answer I think to realize that cash/money isn't really much of a goal of folks this powerful, but that money serves as a veil that obscures the actual wealth and power they do seek and possess.
National banks just conjure money out of thin air, which is then affirmed and actualized by governments that borrow it from them. Upon that affirmation of it's reality, it becomes an obligation to pay on subjects of the borrowing government(s), and during QE is then managed by Blackrock (in the USA) in order to raise stock and bond prices by being used to purchase select assets - which, as @perceptualflaws has pointed out in the OP, are majority owned by the same 'investors' that own the national banks.
This is nothing more or less than a fraud corrupt government enables those 'investors' to commit against subject peoples. We don't get the benefit of the conjured funds, but are obligated to repay them to those that did. Every dollar so conjured thus inures to the 'investors' twice over, plus interest.
It is the obscuring veil that allows corruption and fraud to subjugate peoples to these 'investors' that makes it of value to them, IMHO.
Edit: presently, the real wealth availed these 'investors' seems to be the governmental right to violate the NAP by deploying heavily armed military forces to 'distribute' the Covid19 vaccines into our blood.
Since it's a DNA alteration, it has the potential to transform subject peoples into GMOs with genetic traits not found in nature. It is very creepy to consider what traits such 'investors' would find desirable in their proprietary quasi-human subjects.