As people say, older, frail people need to be exposed to a much lower viral dose than the general population to become symptomatic.
Pneumonia is the highest or one of the highest causes of death in older people - it's inevitable that CV19 will provide fatal to many.
It's is impossible to provide personal care while socially distancing.
Care homes are run on very tight staff ratios. Carers will inevitably be providing care for many people during the course of one shift.
There are huge staff shortages in many care homes, even more so with staff having to self-isolate or becoming ill themselves. This means that there will be different people coming into the home each day/week.
Many care homes are now huge - more people entering a space obviously increases the chances of the virus entering.
Inadequate PPE and not enough of it.
And hospitals were instructed to move older people from hospitals to care homes to 'free up beds, either without testing for CV19 or with no regard for whether they were infected or not.
So one contagious person entering a care home could cause many more deaths than for example one contagious person entering a shop.