A couple of other considerations.
Firstly it's not about what you need in a short period of time, it's about what you think you'll need between now and whenever things return to normal. With no way of knowing whether things will return to something like normal in a week, a month or six months it's easy to see why people prepare for a worst case scenario. Toilet paper in particular doesn't go bad, so it's not as if anyone who does end up with 5 years worth of toilet paper will end up throwing it out because it spoiled. When some voices are calling to get everything open, others are calling to maintain restrictions for a couple more weeks and still others are calling for lockdowns lasting 10 weeks or more, it's hardly a surprise that people take whatever chance they get to stock for the worst case.
On a far more mundane level, the people that used to be at work at now at home. Every single bodily function that required toilet paper that was once performed at work is now being performed at home. That means a huge extra demand for domestic toilet paper. Commercial toilet paper is often of a lower quality and made in much larger rolls, rolls far too big to fit in a domestic toilet paper holder. So the supply chain for regular domestic paper is disrupted due to a surge in demand, even as the demand for commercial toilet paper collapes.
I'm thinking if we can't get more toilet paper before we open our last packet I'll be approaching a local paper manufacturer to see if they will sell me the giant commercial rolls. I can make something to hold it in the bathroom if needs be - it won't necessarily be pretty but it will do what is needed.