> how to do you explain why the UK grew so much faster than other EU nations in the decade before Brexit? Similarly, how do you explain how much worse is the UK economic story after Brexit? It seems exactly the opposite of what you wrote.
Are you sure about that? It seems about equal to me [1]...
In any case, Brexit didn't cause closing the borders; immigration into the UK increased massively [2] (i.e. the politicians didn't deliver what the people wanted). Any negative changes to the UK economy were more likely caused by decrease in trade with the EU... [3] Although COVID makes all these statistics suspect.
[1] https://ourworldindata.org/grapher/national-gdp-constant-usd...
[2] figure 5 here: https://migrationobservatory.ox.ac.uk/resources/briefings/lo...
[3] https://obr.uk/box/the-latest-evidence-on-the-impact-of-brex...