Could it be that men are pigs and that they are more likely to support unjust or unfair systems if it gives them a slight advantage?
As a white male I sure do enjoy the privilege of constantly being the villain of society due to original sin I never done. Love how I'm a pedophile bigot out to pillage and rape every woman I encounter.
you are not a bad person, but you are foolish and for many purposes this is indistinguishable.
Consider it rather like that of the antebellum south. Objectively, white males who did not own slaves did not benefit from slavery. Why? Because of-fucking-course they didn't. They existed in a capitalist society wherein their labor would always be devalued by the fact that someone else could do their labor and be reduced entirely to the minimum sustenance wages. Even if plantations didn't produce enough to entirely wipe them out, they were always being tremendously disadvantaged and it was a sort of invisible tax on what they produced; the free hand of the market dragging down the value of their supply since someone could do it cheaper (since slaves are, well, about as cheap as labor can theoretically get). So slavers had a problem: what if any of these white men noticed that they were being consistently screwed by slaveholders? That their entire lives would be worse because of slavery? What if they got it into their head that maybe they had shared interests with the slaves? Well that would end the entire venture right there.
Hence the ingenious idea: make it about skin color. Make it about an intrinsic biological superiority. Make it "Hey at least you ain't them." See the genius trick there is that not being "them" is free: it means they don't have to give you any sorts of rights or powers or share of the economic pot or quality of life or anything; you already got all you need, you are just automatically morally and ethically superior without any actual requirements. Once you tell that story, you find not only are the non-slaveowning whites not tearing things down; why, they're helping keep it together! They support it! Fight and die to protect it! You might think "Would they really?" and the answer is that when you have a lot of wealth and power you can tell a lot of stories, and especially in the 1800s you didn't exactly have other situations to compare it to, even if you did care what other weird people in far off lands did. No sir you can
enlist them. Make them fight, heart and soul, flesh and blood, to defend their small pile of dirt because it's slightly more than what the others get. And they can be allowed to think themselves peers of those who own more than they could ever dream, without ever partaking in but a small fraction of the power, wealth, etc.
This idea was so strong, in fact, it well outlived the slave system it was created to protect, adapting to fit "new" systems as they arose and took and advantage of conditions. Because hell at least they ain't black, at least they ain't foreigners, at least they're not godless atheists/communists/muslims. I will admit quite freely people tend to fight against
these people, but that's because that's exactly what those who profit
want. Because by doing that, by pointing at these willing executioners of their own will, the profiteers continue the cycle and keep focus away from those who actually benefit.
People throughout all of history have developed ideological systems that privilege their own position; saying that's not any more radical than saying "people generally prefer to be happy"
[CITATION NEEDED]. But the trick here is to subvert this instinct; instead of making yourselves (for whatever variation of "yourself" you come up with, any demographic or distinguishing activity can work) the primary beneficiary, make them the secondary beneficiary. An ideology content to fight for the scraps without realizing it is doing so. If they ever "won" entirely there would be a problem, but since they are fighting against people also trying to live their own lives, they've got a nice stable situation.
It's not even exclusive to capital, the US, and slaveholding; it's been heavily used for imperialist tendencies as well: privilege a group or subgroup, make them willing executioners of the will of the powerful. The Belgians doing so heavily (forcing both to have id cards stating their group, letting only one get higher education, etc.) served their colonial interests, and led to the situation between the Hutus and Tutsis which led to the Rwandan Genocide farther down the line. The Ottomans doing so in the Balkans is why that region remains poor and stuck in ethno-religious infighting that benefits precisely none of them (even long after the ottomans themselves became irrelevant; now others do, kleptocrats eager to distract from other issues). The Austrians privileged the Hungarians, made them equal partners, which immediately recruited them to the task of stomping out nationalism and the rights of minorities all over the Hungarian part of the Dual Monarchy (and being so strong as to eventually hobble the Austrian reformers who envisioned a "TriMonarchy", with Slavs brought up as equal partners; note this didn't not
take away Hungarian privileges except by making them merely
equal to slavs, and
that was enough to lead the hungarians to oppose it strongly and sink the whole plan.)
The process of bringing in a group as a equal partner or alternatively privileging one over the other is about as old as the roman empire at least; Julian the Apostate, to try and turn back the tide of Christendom sweeping the empire, enacted a series of reforms to encourage local religious practices over state practices (whereas prior they were functionally one and the same, barring cases like Judea with Jews being rather unfond of the synergistic Roman Imperial Cult); had he not been assassinated and had longer to do so he might well have succeeded. This is a historical fact throughout the ages!
Recognizing this, in and of itself, helps fix it. It's not personal. It's not about you, a white straight man, you are not the profiteer. You may gain some small benefits but they are minuscule in comparison.