Well, originally, they weren't necessarily white people. Patriarchal dominance hierarchies arose in many places all around the world about 5k years ago, spreading in part, because they were so disruptive.
The following is a bit of an oversimplification because agriculture didn't always immediately equate to dominance hierarchies, but it's still a good, broad survey of some of the elements that led to this shift.
The social dynamics only began to change as greater personal property that came with a larger reliance on agriculture began to be a factor. Combine this with a wave of natural disasters and incursions from more warlike Proto-Indo-European tribes, and a new more stratified type of social organization arises. This included not only a gendered power differential but a whole new class system where none had existed before.
The following excerpt from an article in the World Economic Forum explains quite well how this came about:“Labor roles became more gendered as well. Generally, men did the majority of the fieldwork while women were relegated to child-rearing and household work.
Without contributing food (and by association, without control over it), women became second-class citizens. Women also had babies more frequently, on averageonce every two years rather than once every four in hunter-gatherer societies.
Because somebody had to have control over surplus food, it became necessary to divide society into roles that supported this hierarchy. The roles of an administrator, a servant, a priest, and a soldier were invented. The soldier was especially important because agriculture was so unsustainable compared to hunting and gathering. The fickleness of agriculture ironically encouraged more migration into neighboring lands in search of more resources and warfare with neighboring groups. Capturing slaves was also important since farming was hard work, and more people were working in these new roles.
This division of labor and social inequality had very real consequences. For instance, while the majority of people had disastrous health compared to their hunter-gatherer ancestors, the skeletons of Mycenean royalty had better teeth and were three inches taller than their subjects. Chilean mummies from A.D. 1000 had a fourfold lower rate of bone lesions caused by disease than commoners.”
As time went on, white people built on their ability to make Might Makes Right pay for them, and they continued with colonialism and other types of dominance hierarchy subjugation, but these hierarchies also exist in Asia, in the Middle East, in Greece and Rome, etc., so it's not really a white person thing, except that we seem to be particularly good at subjugating others for our own benefit.
This story has a bit more nuance and is perhaps more than you really want to know, but I'll include it just in case.
