In my area, that's closer to 6 months supply. I went to Costco right after the coronavirus data hit the mainstream news and before Costco put limits on basic items like TP, and a lot of people were buying 2 packages of TP. In fact, one of the Costco stores had to close because of a fight over TP. Each package at Costco has 36 rolls, so if you use 1 roll/week, that's well over a year's supply. For my family of 4, a 36-pack lasts >6 months (probably closer to a year, I haven't bothered to calculate it), and we picked some up about 2-3 months ago, so we didn't bother buying more.

That's why it's so weird to me that people are buying so much. How long do people expect this to last? I'm guessing it'll be resolved within a couple months in most places, so what's the point in buying >6 months worth of TP?

Honestly, I think everyone with means should have 1-2 months of basic necessities on hand in case of emergencies (job loss, natural disaster, etc), especially for shelf-stable stuff like TP and soap. However, the time to stock up isn't when an emergency happens, but after an emergency happens (presumably your stock is a bit low).