So so many people like this. The fairly recent one of the wetsuit man too, plus cases from the 70s when you would reasonably expect people to still be alive who knew the person then.
Some people lead insular lives, but they still go shopping, they still walk out of their front door while neighbours are out the front gardening or whatever, it is very hard to be in a position where no one knows you even if it’s just ‘I’ve seen him in the corner shop buying milk but I don’t know where he lives’.
You'd think bills not being paid would be noticed, but everyone has direct debits, and if you’ve got money or benefits going in then the bills still get paid. That’s what happened to the woman in the flat in London, her benefits carried on for a few years.
Or maybe he was a criminal, and people do know who he is/they are (thinking of other cases) but they have no interest in it. The police do say ‘allegiances change’ so people sometimes come forward decades later.
I remember some witnesses came forward for something a few years after a crime, they didn’t realise they had witnessed anything relevant and were on holiday, and the publicity had not reached their corner of the UK.
Also there is a case of a Bulgarian woman (?) who was dead in her flat for decades, no one missed her ☹️.
Sometimes people just think they haven’t seen someone for a while and they must have moved away.