The Canadian brand of nationalism that multiple generations of Canadians grew up was largely created by the Pearson/Trudeau era of government: multiculturalism, bilingualism, peacekeeping, the idea being a moral leader on the world stage, the belief that “the state has no place in the bedrooms of the nation.”
The challenge Harper tried to overcome was this version of Canadian identity that was so tied up to Liberal policies- right down to the national anthem, flag, and charter. It’s why you had Conservative MPs insisting on calling Canada Day “Dominion Day” and so much interest in the War of 1812- it was an attempt to reset or at least nudge the Canadian identity towards something that wasn’t created by the Liberals.
Obviously there are huge differences between Trudeau, and Trump, and Brexit, but they all appeal in part to the belief that things used to better. They appeal to a nostalgia for a version of each country that was stronger, more respected, treated its people better. It’s a promise that things were better, once, and after this vote, they will be again- regardless of whether any of that is true.