Trump is but a continuation of the trend, latent in American political culture throughout its history, but first brought to the fore in the post WWII era right after 9/11, to ignore multi-lateral collective problem solving international institutions and to blatantly lie to override considered educated opinions in pursuit of policy objectives.
The us vs them rhetoric that Bush used in the speech to Congress, the clash of civilization narrative more commonly used by the conservative circles at the time are really just more erudite sounding and politically correct versions of much more degenerate “shit hole” crass dog whistle that trump would use 15 years later. but they serve the same function. They are both aimed primarily at pre-1960 white men’s insecurity about multi-culturalism, and collaborationist approach to problem solving gradually robbing them of their privileged position, whether that position stems from their position in their own country, or their country’s position in the world.
It's not just multi-culturalism.
It's also female empowerment in education and the workforce, and the resulting imbalance between the sexes.
Historically, every male was much more educated and wealthier than any female - which made pairings easier.
But now, females have much higher educational attainment levels than males in US high schools, and account for 60% of college students in the USA
It means there are a lot more educated and higher earning women - who are unable to meet a partner who is their equal.
And these days, women don't need to settle.
At the same time, in the USA, 1 in 7 men have an IQ below 85.
That represents the cutoff for being able to perform any sort of job.
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So what is the result for men?
There are a significant number of low-IQ men in the USA who are unemployed or in low-wage jobs.
They are largely overlooked in the dating market.
The average man in the USA really struggles in the dating market, because the available women tend to be more highly educated or higher-earning.
So you can see where a lot of white male anger comes from, which Trump and the Republican Party tap into.
A similar dynamic occurs in other countries around the world, including in China.