The establishment were pro brexit because of fear of the incipient socialism implied by the social chapter - another layer of regulation, of benefit to ordinary people, particularly "the working class".
Press corner
How to persuade people to vote against their own interests?
Easy peasy - just do what the main stream media has always done to control the mob; persuade them to hate each other. Hating foreigner workers was tops, particularly Romanians.
This is what the MSM do. They lay out an organised hate programme every day. Foreigners, immigrants, the unemployed, asylum seekers, gypsies, students, lefties, Corbynists, media studies, single mothers on benefits, black people, Jews, trade unions......etc etc.
This is what they have always done since 17C or earlier, with the details of the list varying through history - "dissenters, antinomians, witches, catholics, beggars, itinerant preachers, agitators, conjurors, pamphleteers, anabaptists" and so on.
Add to the mix the crackpot conspiracy theories; Qanon, paedophile rings, the Great Reset, covid as a sinister totalitarian confidence trick, terrorists, then it's no wonder that a lot of people are going around totally confused and getting angry.
Then smart alecs like Farage or Johnson will say "follow me chaps everything will be all right".