It's actually very simple. There was a nationwide shortage of toilet paper in the US due to disruption of supply chains, TP industry workers unable to work due to being sick and, in the early days, quarantines of exposed people, hundreds of millions of people and their children sheltering at home and using the home bathroom facilities rather than workplaces and school toilets. If you were stuck at home with your five children who normally would be at school all day, then, yeah, you needed a lot of toilet paper. Your customary purchase of 10 rolls per week suddenly wasn't enough TP to last your family for a week. You needed three times or more than that amount. So, yeah, some people hoarded TP.
We see the same stocking up/hoarding behaviors every time a severe weather event is forecast. Food, water, pet food, baby supplies and paper products quickly disappear from stores. Intelligent and informed people who routinely live with extreme weather know how to stay supplied with essential products so we are always prepared. I live in an area of extreme and violent weather in a rural location, and the nearest "decent" store is at least 10 miles away. I try to ensure that I have on hand whatever we'll need for a couple of weeks rather than risk finding empty store shelves in an emergency. It's not hoarding, it's simply being prepared for a very predictable situation.