This is a form of mass hysteria. The media reports on some silly commodity like toilet paper having run out in one store (maybe they didn't get their delivery,

This is a form of mass hysteria. The media reports on some silly commodity like toilet paper having run out in one store (maybe they didn't get their delivery, unrelated to coronavirus at the early days). People take this signal to mean that toilet paper is going to run out. Now, afraid of being left without toilet paper, and worried that others are hoarding it for a reason they do not yet understand, others go to buy it. It's the same reason why people start buying ridiculous things when a celebrity is seen wearing them. People look at it, don't understand what's going on, but don't want to be left behind, so demand increases irrationally.