With the world shutting down the companies that supply those kinds of places had a warehouse full of inventory and most of their usual customers either were entirely shut or going through a lot less product.
I'll wager your grocery store called one of them up and got a few pallets to resell, creative move on their part.
It didn’t take a big demand increase to start seeing gaps in shelves, and once that happened a degree of panic took hold and even though there was plenty in stock in warehouses, it wasn’t able to be distributed fast enough.
The difficulty is that the big supermarkets have got their supply chain down to a fine art and it only takes a small fraction of people to start buying an extra here and an extra there for it to start having an impact and they then have to struggle to keep up.
I remember a couple of years ago when we had a lot of snow (for England) and it kiboshed the supply of things like milk and bread for about a week, even once all the roads were clear.
You only need a chunk of people to buy a few more toilet rolls than they usually would "just in case" and suddenly the shelves are empty.
Plus the commercial domestic imbalance.
[1] https://www.census.gov/library/stories/2021/03/many-american...
[2] https://www.businessinsider.com/half-of-americans-used-1400-...
People were afraid they won't be able to buy bread, so they bought flour and yeast... then bought bread, and eventually threw away the yeast.
I think this was the root cause of the toilet paper shortage. People who normally spend a large portion of the day at the office were now spending that time at home. There was a popular viral video at the time of a man driving around on a forklift in a warehouse full of toilet paper laughing about the shortage, but it was all commercial toilet paper not what you would use at home. Anecdotally I noticed a correlation between the level of traffic on the freeway and the amount of toilet paper on store shelves. When the freeways were empty the shelves were bare and as traffic started picking back up the shelves started replenishing.