It's not some extremist on YouTube, disinfecting your groceries was the official recommendation of many countries worldwide, including most of Europe. I couldn't say how many people actually followed the recommendation , but I would bet it's way more than a tiny number.
There was a period near the start of the pandemic, especially while the medical establishment was trying to avoid ordinary people wearing masks in order to help stockpile them for high priority workers, when a lot of emphasis was put on surface contact.
If it's extremely important to wear gloves and keep sanitizing your hands after touching every part of the supermarket, it stands to reason that you'd want to sanitize all of the outside packaging that others touched with their diseased hands as soon as you brought it into your house. Otherwise, you'd be expected to sanitize your hands every time you touched those items again, even at home, right?
Of course, surface contact is actually a very minor avenue of infection, and pretty much limited to cases where someone has just sneezed or coughed on a surface that you are touching, and then putting your hand to your nose or maybe eyes or mouth soon after. So sanitizing groceries is essentially pointless, since it only slightly reduces an already very small risk.
