I think a shift in consumer behaviour over a period of years. Alcohol can be bought in bottles from the supermarket and drunk at home. Younger people tend to drink less. Covid shut some pubs forever, but the structure of the industry made it increasingly difficult for an independent landlord or a tenant to make money.
There used to be a pub on every street corner. CAMRA says beer tax, business rates and PubCo reform.
https://camra.org.uk/take-action/
Most of the successful pubs are often
restaurants as well. But others become housing developments, blocks of flats, offices or convert to another form of business. Often they are demolished.
That 42,000 is measured over a long time.
https://www.statista.com/statistics/310723/total-number-of-pubs-in-the-united-kingdom/ says 14k pubs were lost from 2000- 2022.
The Telegraph and
The Guardian agree for once, pubs are in decline and it is hard to stop this. (I've linked to two journalistic pieces.)
The Butcher's Arms I mentioned was owned by an elderly lady. Her relative inherited the pub, but perhaps understandably didn't want to run it and it is now a small housing development retaining much of the original external features. In its glory days it served the thirsty salt workers and farm workers. The cider is a memory. I drank two bottles of Dunkertons with my meal last night at a restaurant, tasty but carbonated and an entirely different product to draught.