I start this by saying I was born in and lived in the Medway towns until I was 26.
It did not surprise me at all that Medway was hit so hard and continues to be
For a long, long time, it's been a very badly off area. Schooling is pretty crap across the board and many in my time at school left either with very low prospects or very badly educated. I have friends who left at 16 unable to read and it went unnoticed. I myself have only very basic maths skills to this day, probably on a par with infant school (which yes is embarrassing as fuck).
There is huge crime and drug issues (it was nicknamed "Brown Town" in the nineties as it was the source of the cheapest crack and heroin in the south east).
There is a huge amount of immigration as well and many have English as a foreign language. Many are hiding from the authorities so if they do get ill they won't seek help.
The local hospital has been marked as failing by the CQC for a number of years and one of the biggest healthcare companies responsible for several GP surgeries has recently been banned from operating due to being worse than inadequate, leaving quite a high number of residents with no GP surgery as a result, something which has been ongoing for months and probably not helped by the pandemic.
With all those issues, and mates who live there suggesting that you very rarely see anyone wearing a mask properly if at all, plus quite a big proportion of underlying illness and old age, along with poverty and you've got the perfect situation for a huge spike.
Now, I haven't said this to be offensive to anyone who still lives there, as I say I still have family and very good friends who live there who have said how bad it is (including a nurse) so apologies if I'm wrong here.