There has been a long-term trend -- both within psychology and in society -- to ignore that people differ in their personalities. In social psychology, the belief that what you see which is distinctive in a person represents something about them, rather than the situation that they were in, was called "the fundamental attribution error."  One great advocate for this was Ken Gergen -- whose claims that there is no such thing as personality I refuted in Psychology Today.  Here is a description of his work and that of other, similar, psychology know-nothings.
Two things made evident by recent history have beaten down the theory that personality means nothing.  The first is Donald Trump's indelible way of thinking -- how he filters every bit of his experience through his mindset, such that nothing ever dissuades him from his initial prejudices and delusions.  Donald Trump's immunity to evidence is the ultimate sign that people's interior monologues, with them since very early in life, determine how they not only see, but how they experience, the world.
Lately, the New York Times has become aware of Trump's ineluctable perspective, detailed here by Michael Shear, prompted by Trump's interview in Time where he doubled down on every hare-brained conspiracy theory he has ever held.
Shear doesn't actually penetrate Trump's personality, so much as he notes Trump's cognitive style and its built-in errors.  These traits include that Trump regards himself as "an instinctual person" (i.e., he devalues thinking and evidence), that in announcing one bizarre theory after another he is "just quoting" (i.e., Trump accepts any crackpot source as proof of his own delusions), and that he "knows how life works" -- that is, his business and electoral success proves that his crazy slant on life is true, and why would he change it.
At the other end of the political landscape, the Times columnist who most respects and references academic psychology, Thomas Edsall, reviews the evidence ("What does it take to climb up the social ladder") that social class (based on income level and parents' education), in good part, although not exclusively, yields the "noncognitive skills" that determine people's destinies.
These ideas form the basis for the work of Richard Reeves, who has analyzed the ways in which social inequity persists, is indeed baked into our social system, and especially how character traits such as persistence and "prudence" lead to superior social and economic attainment and outcomes.
Even writing these words down no doubt strikes some/many readers as racist and classist, and indeed disregarding and opposing such arguments forms a major basis of the Democratic Party's outlook (if not totally its platform).  However, the enduring consequences of ignoring these things has produced what is beginning to appear to be a perpetual social disaster -- one that Donald Trump has built his success on.
Here is Edsall's summary of this research and history with my italics added:

First, the spectrum of noncognitive skills and character strengths are a major factor in American class stratification. Whether these factors are more or less important than extrinsic forces like globalization, automation and declining unionization remains unclear, but changing family structures are evidently leaving millions of men and women ill-equipped to ascend the socioeconomic ladder.
Second, neither religious leaders nor practicing politicians nor government employees have found the levers that actually make disadvantaged families more durable or functional. As a corollary, the failure of government efforts to affect or slow down negative developments has left an opening for conservatives to argue that government interventions make things worse.
For liberals and the Democratic Party, the continued failure of government initiatives to achieve measurable gains in the acquisition of valuable noncognitive skills by disadvantaged youngsters constitutes a major liability.
This liability played a role in the outcome of the 2016 election. Throughout the campaign, President Trump repeated comments like this one:
"The Democratic Party has run nearly every inner city for 50 years, 60 years, 70 years, and even more than 100 years they have produced only poverty, failing schools, and broken homes."
This and related charges will continue to dog Democratic candidates in 2018 and 2020 unless progressive policy advocates can find ways to more effectively highlight and capitalize on the ample supply of character strengths evident everywhere among America’s poor. This is extraordinarily important.
Advocates for the disadvantaged must also highlight and capitalize on the many demonstrably effective antipoverty solutions already well known to the academic, research and nonprofit communities. Without better funded and better crafted organization and advocacy on behalf of the poor, the propaganda and accusations now emanating from the right will ineluctably reshape the law of the land — and once institutionalized, such "remedies" could prove staggeringly difficult to reverse.

(I repeat, the above paragraphs are the words of Edsall.)
This is a highly pessimistic conclusion.  It finds the sources of our growing inequities within the people at the bottom of the social scale (I hear readers shouting "That sure is a convenient point of view for well-heeled New York Times writers"), that our refusal to believe that personality traits persist hamstrings liberals while, paradoxically, justifying the disinterest in social remedies that marks the Republican Party, and that things are spiraling evermore in this downward trajectory.
And, incidentally, this same perspective applies to addiction where, as I note, our biochemical and brain fixation has accompanied our drowning in new depths of despair.
So disregard these ideas at your -- and America's -- peril.