For me, when someone says

"it is uncertain whether earlier intervention in care homes (or more PPE) would have greatly reduced the casualty numbers"

it is the word 'greatly' that leaps out. What is that supposed to mean? I imagine a conversation saying

"Sir, if we can provide more PPE we can cut the casualties by 5%"
"Only 5%? Not worth doing then."

Why insist on 'greatly reducing'?