I imagine it's helped that they are admitting more moderate cases now for the oxygen like Boris had. In early days you'd have to be more poorly, blue lips and gasping and at that point it was likely to be a poor prognosis anyway.
It took a few weeks to clock that moderate cases were dropping off a cliff with no notice, if memory serves as you could go from being unwell to suddenly in crisis, but as criteria for admission was so high people ended up dying at home. Once they allowed more people in to hospitals at an earlier stage on they could pull more people through.
From my understanding this is why Germany's death rate is so low. They had corona taxis and treated people with oxygen at home from early on in their illness.