When the Industrial Revolution began in Britain, in the late 1700s, there was lots of money to be made by investing in factories and mills, by opening up new markets, and by gaining control of sources of raw materials. The folks who had the most money to invest, however, were not so much in Britain but more in Holland. Holland had been the leading Western power in the 1600s, and its bankers were the leading capitalists. In pursuit of profit, Dutch capital flowed to the British stock market, and thus the Dutch funded the rise of Britain, who subsequently eclipsed Holland both economically and geopolitically.
In this way British industrialism came to be dominated by wealthy investors, and capitalism became the dominant economic system. This led to a major social transformation. Britain had been essentially an aristocratic society, dominated by landholding families. As capitalism became dominant economically, capitalists became dominant politically. Tax structures and import-export policies were gradually changed to favour investors over landowners.
It was no longer economically viable to simply maintain an estate in the countryside: one needed to develop it, turn it to more productive use. Victorian dramas are filled with stories of aristocratic families who fall on hard times, and are forced to sell off their properties. For dramatic purposes, this decline is typically attributed to a failure in some character, a weak eldest son perhaps. But in fact the decline of aristocracy was part of a larger social transformation brought on by the rise of capitalism.
The business of the capitalist is the management of capital, and this management is generally handled through the mediation of banks and brokerage houses. It should not be surprising that investment bankers came to occupy the top of the hierarchy of capitalist wealth and power. And in fact, there are a handful of banking families, including the Rothschilds and the Rockefellers, who have come to dominate economic and political affairs in the Western world.
Comment: It's a simplification of the world that is the product of a psychopathic mindset. Psychopaths always rise to the top, no matter their background as doctors, leftists, humanitarians...