One of my favorite facts in history comes from the era of the Crusades. Who benefitted? Why, the arms makers of northern Italy who equipped both sides did.
Sorry, but that is wildly unhistorical.
Bankers can “run things” only when there is a long-term political system that protects their profits against expropriation.
That system has not existed through most of history. Indian, Chinese and European history is filled with instances of “powerful” bankers being executed and/or having all their wealth confiscated when they fall out with the real rulers.
They didn't run things from '29 to '45.
And that was the problem.