I'm Northern, I live in an ex-mill town in a Labour region (Labour MPs and Labour councils), and I've been involved in politics for twenty years.
The real rot started under Blair. We had high hopes for Blair, foolishly believing that we might see investment and change in post-industrial areas of recividist unemployment. We saw nothing of the sort. After devolution failed with the NW vote, nothing else happened. Instead, what we got was extraordinary levels of immigration into areas that neither had the housing stock nor the jobs nor the capacity to cope with it.
For example, back in the early noughties, there was a significant issue with British youths being able to qualify as tradesmen because the NVQ route required an apprenticeship. Nothing was done to correct this issue; instead, the Labour government dealt with shortages by importing EU tradesmen. Traditional Labour voters noticed this because it was their sons unable to qualify.
Incidentally, it was also around the time of EU expansion that Labour ditched the requirement for a foreign language at GCSE. I have always felt this was an almost malevolent move designed to hobble British working class youth in the face of freedom of movement. Where could they go and work in Europe? They had NO foreign language skills.
Then came Brown and bigotgate. It became clear then that Labour had no empathy with the situation that many working class Northerners found themselves in. They were just "bigots" and "racists", regardless of the fact that the only thing some of these communities had were the fact they were communities with a shared history and language, and were all in the same boat. Mass immigration took that away from a lot of areas.
The racism charge was also beyond ridiculous, considering that many post-industrial areas had settled postwar immigrant communities and a significantly higher proportion of mixed marriages than you find among the southern middle-classes.
But then the liberal elite had form for that. The Parekh report even had the audacity to tell white working class mothers they were racist to their own beloved mixed-race children, ffs.
Add to that, the decades of Labour council governance and the Blair and Brown years, which delivered very little to Northern areas. Demographic pressures were ignored. Infrastructure overcapacity was ignored. There are areas in my region that have a worse public transport infrastructure than they had in the 1880s. House prices went through the roof in areas where most people lived on NMW. Meanwhile, everything just got shitter and shitter. Towns that were pleasant in the 90s turned into shitholes. And then Labour local councils sat back and let young girls lives be ruined because they were scared to challenge metropolitan narratives about multicultural Britain.
No one stood up for the Northern working class.
Then came Brexit. For the first time in a long time, Northerners in traditional Labour areas got the chance to register their anger against the political classes without having to vote Tory. This is THE important point here. That is what the referendum gave Northern working class areas: the chance to register their anger without making the move to the Conservatives, which would change how they had to think about themselves.
And Labour blew it. Along with the LibDems and the establishment, it basically turned around and called these voters scum. That was the nail in the coffin for the traditional Northern Labour vote. Why vote for someone that hates you? That blatantly disregards your opinion? That calls you stupid? And the Brexit reaction made clear something they had suspected for a long time: Labour loathed them.
Even for Northern remainers, it was a shock. Labour was calling people who were their neighbours, friends, family members and co-workers "scum" for voting to leave the EU, and doing it in such a way that the accusation spread to all Northerners.
But Boris, well, Boris acted like Northerners' opinions on Brexit were worth something. He made an effort, unlike Corbyn. So, as Labour didn't want those voters and had made it clear, he got their votes for the first time in a very long time. After all, those voters had nothing left to lose.
And here we are. A Tory landslide.