I think it's many many things. No beds in the hospitals means 2 things 1) a&e bays are full, no space to assess patients and 2) a&e is full of sick patients requiring a lot of attention. Beds have been gradually reduced in many hospitals across the country for years now
You also have I would say a greater awareness of health problems now. And people like to get checked out to be on the safe side. For example an infection means risk of sepsis means A&E. Without actually thinking 'do I have signs of sepsis'
There is also a difficulty accessing primary care. I myself have been directed 3 times in the last year by my GP to A&E for things I know did not need A&E, because I had a temperature or a cough and it maybe covid. You cannot properly assess over the phone anything but the most basic health problem, maybe things like a UTI, but anything that requires looking or examining needs to be seen in person. Sadly I have seen a couple of cancers missed because of Telephone appointments. You risk missing things, patients aren't always the best at describing their symptoms- the problem is your well spoken, well educated patient will probably be okay, but I think this can disadvantage patients who arent in their category. There are also patients who over egg symptoms and many patients who don't want to make a fuss so under egg. You miss so much over the phone.
I think there is now a fear around difficulty accessing a GP as well. I frequently see patients who have been seen by their GP, but they weren't happy with the outcome so go to A&E because they think they won't be able to get back into the GP. In many cases the patients do need to go back to their GP but a lot of this work is now falling back to hospitals
But then we also have an aging population, and a population of elderly people who have had nearly 2 years of reduced contact, often living alone. Loneliness leads to mental health problems which can worsen things like dementia. They haven't been able to stay active, and keep their mind active as well. They've not had the care maybe they would have had without covid, or the family visits to notice when they start to need a but more help. Plus a real social care crisis leads to a melting pot of falls, and ill elderly people that get stuck in hospital
I think you also have to differentiate between 20 hrs to get assessed, and 20 hrs in a&e which may include investigations, wait to see specialities, waits for a beds, waiting for patients to sober up etc.