As far as I know:
1) The last generation educated under pre-postmodern teachers and professors has been exiting participation (people are now in fifties to sixties or later). The generation of postmodern teachers and professors have taught this generation, at the same time parents have over protected, and immigrant labor has eliminated demand for youth labor. And has communicated with smart phones rather than learned to drive, earn money, and integrate and cooperate with people holding different (more mature) views. This generation was not raised to be independent functioning adults, but pets, just as (beginning in the 1970s) relationships were not economic but ‘friendships’ which led to the higher divorce rates and the nearly ubiquitous ‘starter marriages’ that compensate (expensively) for failures to prepare children for adulthood.
2) The (“pet generation”, Millennials, “I-Generation”) began entering the consumer customer base, entering the academic customer base, social media customer base, and graduating into the young-underpaid-wanna-be-journalist base, each market appealed to these new consumers.
3) The same access that gives the alt-right influence on the internet gives the politically correct access on the internet. So the pet generation and the responsible remaining generations (the pet generation ends at 95 according to Haidt).
4) The social media platforms and web news and entertainment sites are primarily populated by these people young (pet generation) individuals and they are creating demand in every market including the political market.
5) The victim narrative plays well for first and second generation immigrants from underclasses, who have no chance of rotation out of the primarily genetic middle classes as did previous generations, because the post war economic advantage of labor has been neutralized by the universal adoption of literacy, education, consumer capitalism financed by fiat money and state credit capacity, and vast populations now competing with american labor.
6) These factors are all coinciding with the one-to-one replacement of whites with hispanics, and the recognition by the white working classes that without elites they will be left behind to suffer equality with the new underclasses. Hence the increasing identification of race and party.
I dunno. This is all pretty well studied material. The problem is – it’s contrary to both new-left and old right narratives. The republicans assumed as good fools of the enlightenment that the top and bottom would move toward the middle. It would have happened but immigration has masked the various immigrant state economies, with those lacking immigrant cities collapsing under the weight of New Deal and Great Society (Soviet style) relocation programs. Even those immigrant cities would collapse if not for debt capacity.
Why this is difficult to understand is always beyond me.