It's not particularly extraordinary because the UK's economy is dominated by services companies, and the EU single market never really made progress for services. They only developed and enforced a single ruleset for goods. Attempts were made from time to time to liberalize the market in services but usually failed because it would have benefited the UK at the cost of France/Germany, whereas for goods it was the other way around.

That's why exports to the EU haven't changed much (see my other comment). Imports did fall, but that the UK continues to import from elsewhere so it's unclear why people in Britain should care. The EU lost an export market, the UK didn't really (because the EU rules weren't benefiting that market in the first place).

This is the sort of thing I mean - there are a lot of people who very much want leaving the EU to be a disaster for long term ideological reasons. To determine whether it actually is or not requires a holistic analysis that goes well beyond economics, but at the moment even establishing basic economic facts like "inflation is not caused by Brexit" is apparently hard.