What people don't seem to realise is that a lot of things that have been allowed to do during the pandemic are relaxations so that people can have some semblance of normality and the country as a whole can keep going, in some respect.
Ideally everyone would have sat at home and had contact with nobody and the pandemic would have been over months ago. But obviously we still need basic services (food, medical, police, heat, light and communications etc) to continue, so people are allowed to go to work, but not socialise and should minimise contact with other people, as far as possible.
But just because people are allowed to do these things doesn't make it safe, and any contact with other people carries a risk, but that risk is balanced against the detriment if there had been no power, no police, no medical services, no food, etc etc.
So at Christmas, just because people were allowed to mix on Christmas Day, it wasn't because it was suddenly safe, it's just that the government knew that people would do it anyway, so they gave guidance on how to minimise the risk while having something of a Christmas. The initial 3 households/5 days relaxation was obviously far too generous with rising cases and new variants, hence why it was scaled back.
But it was fairly obvious what was going to happen. Millions of people mixing indoors with family was bound to cause some tragedies like this, it was inevitable. As illustrated on this thread from mid November last year, when we were in lockdown 2 and talking about what we thought would happen about Christmas.
I said, and it has pretty much played out as such:
*Shops open again 3rd December.
Pubs and restaurants open a week or two later.
Schools closed for 3-4 weeks between mid Dec and early Jan.
Restrictions eased completely from Christmas Eve to NY Day with the warning 'be careful'. Everyone spends the entire Christmas period as if covid doesn't exist.
Huge spike in cases early January, back to full lockdown and sad face stories in the tabloids in late January about families with multiple bereavements because they had mass gatherings at Christmas because they were allowed to*
And here we are.