It's a large event, yes, but a web-based business should prepare for an event they know is coming, and be able to scale servers in response.
Maybe they are doing this and it's still not enough, maybe they are doing nothing but watch their servers redline all day, waiting for traffic to die down in a few days.
For many people this is their first experience with Paizo, by not being prepared for that traffic, they have made those people's first experience a terrible one.