I'd heard people refer to it in passing on the main boards several times but thought it was about sensible prepping, like for people who live in remote areas and might get cut off if there's heavy snow or floods, or getting a bit extra in before the Brexit price increases or whatever. Then someone mentioned it following the invasion of Ukraine and I had a look out of curiosity, and people were discussing how to build nuclear bunkers in their back yards.Have you ever visited the Preppers board? Even before we had heard of covid they were stockpiling- they did it during the "millennium bug" and for the Ukraine war. Some of them have multiple fridge freezers and rooms just to stockpile in case of an apocalypse.
Unrelated, there's an AIBU thread about OP's boyfriend having inappropriate boundaries (in her opinion) with his female friends that's getting uncharacteristically sensible responses. It always makes me laugh when people on there think that once you're in a relationship you should have no contact with anyone you've ever had any sexual involvement with, even if it was just an unrequited crush or a drunken ONS fifteen years ago. Most of my friendships date back to my uni days - if I cut off everyone where there'd ever been feelings on either side I'd be living like a Trappist monk.