How?
Brexit was turned into a grievance vote. Some people voted for Brexit because they didn't get their bins emptied often enough. Surveys at the time showed that only 7% of the population voted based on issues that were actually about the EU itself. Anyone who tells you differently is lying.
No one defined what the shape of Brexit would be. It was the policy of the leave campaign that was shaped by Cummings. But equally those who set up the vote and were remain also failed to define Brexit. Its not a remain v leave thing. Its a basis mismanagement issue. Cummings is effectively the Godfather of this.
The next few years were a battle to define Brexit. The whole of parliament fought to impose their preferred choice. But May couldnt get a majority on any option even with free votes without party lines. Her Deal was the last opportunity for a sane solution. It got shit canned by everyone who failed to see the point in politics which was such a tipping point.
So she called an election and then got worse and eventually she had to resign and there was another election and that turned into voting for the figurehead of Johnson. Johnson policies of going for the red wall were a continuation of those grievance voters. He chased them. He stole actual labour policy to do it (which then got shit canned too)
Even he at times struggled to unite the party. Then covid happened and then Ukraine happened.
These both laid bare years of unpreparedness and attention to food and energy security and sparked an economic crisis. This was compounded by the inadequacy of the Brexit deal. To date the Northern Ireland protocol remains a disputed point. Many warned about this prior to the ref.
And so Johnson never actually delivered on solving any of those grievances and then got sucked into a party standards row.
Then Truss came along. She decided that her vision for the future was aligned with the hardest line libertarians within the party in terms of economics. This version of Brexit Britain was the one talked about long ago as being the one most wanted by nefarious oligarchs and millionaires but massively out of step with the public. To the point of insanity. But Truss knew better. These nut jobs are all about things like disaster capitalism. Again many warned about this. None of which are in the interests of the public at large. So Truss has actually already achieved at least part of what they wanted, which is to fuck over the uk for the benefit of the super rich. That not even the well off middle classes who might earn £100k a year who have been turned into a weird kind of bogee man. It's actually worst than that. It people who are worth far more than that and are even smaller in number.
Worst bit is I think Truss was oblivious to what would happen. She's demonstrated she has a complete lack of understanding of how politics works. Her attempts to save her own neck yesterday and today are insane and in line with sheer incompetence. Even more so than not understanding the financial markets. Truss has been doing this job at the highest levels for 10 years!
It was never about Brexit. Because Brexit in practice was never really about the EU. It was a device to capture grievance voters who otherwise would vote against the sitting party. It required grievances to be fixed. No one did and then two black Swan events fucked us over even more.
And that's the story of how we got here.