I think what one commenter said below the article was much more perceptive than the article itself, which simply blames rapid ethnic change and goes no further: that it’s still the economy, but it’s how the white vote perceives their economic problems coming from that is key. The article conveniently ignores all the evidence concerning the number of people who voted for Brexit, citing immigration as the key reason, despite living in areas barely affected by it.
One of the big problems is that there’s been a levelling out across ethnic and gender groups amongst ordinary people of economic and social circumstance, whilst the elites have gotten increasingly richer and more remote. It’s not surprising that working class white males notice and fiercely dislike this the most, and that anger has been channelled into hating immigrants.