The article is indeed just putting forward a hypothesis. I don't claim to have proven anything with it. Your historical observations are just the sort that would be needed to test the strength of this explanation.
I'd add a few relevant points. First, you leave out the possible role of psychopathy even in the more egalitarian Stone Age. Although psychopathy would indeed have been a nuisance in inter-human relations within the small tribes, that recklessness and lack of empathy would have been instrumental in the hunt for wild animals, to help overcome the highly intelligent social mammals' aversion to killing. So psychopathy (the switching off of empathy and socialization) may have a biological basis, which accounts for the difference between toxic masculinity and femininity, assuming there was a division of labour in prehistory.
As for Christianity, I agree that brotherly love is antithetical to any conscious celebration of psychopathy. However, Jesus's ethics were only nominally relevant to Christendom. The Church wedded itself to the patriarchal Roman Empire, and had to rationalize that imperial inheritance despite Jesus's anti-establishment sentiments. So that's a complicated picture.
Regarding Australians, you seem to have forgotten that I dismissed the genetic aspect of race in my one paragraph on Whites vs Blacks. I'd talk only of cultural differences, at that point, so the isolation of Australia might have impacted White Australian culture, making it less individualistic.
Elsewhere, I talk about how the economics of laissez-faire capitalism fostered psychopathy (links below).
I can see how poor people eking out a living in ruthless industrial societies might indeed resort to cut-throat practices to survive. It's the individualism there that makes for that resentment. A collectivist society would have more of a welfare state or a social safety net. The social Darwinism that contributed to early industrial Europe provided a rationalization for the toxic masculinity of the aggrieved poor.
Who says all psychopaths have to be winners? Some can be resentful losers who figure in an individualistic society that's envisioned as a Darwinian survival of hunters in a competition for wealth and status. The losers may be aggrieved because they feel entitled (even as privileged "Christians" who take themselves to be on personal terms with God), but their privileges aren't being honoured in society. Of course, Jesus said his followers should be poor in spirit and should expect to suffer in the present age. But modern Europe shifted to secular humanism, which took as paramount our pride in our individual merits (since the second coming had been delayed for two millennia).
