I suspect that this is a really clever marketing campaign as I am sure it will significantly boost their web ranking due to the surge in traffic.
Yes, it's that plus a good load test on their servers. They did it once, then did it again the next year, and it seems to have turned in to a tradition now. They've been doing it for a few years and every time they improve their software efficiency, although last year I think they got it right so I'm not sure if there was as much left to improve this time.
How did they handle the load this year? Last year you were lucky to get one page request through in five minutes for the first few hours, then they fixed what was likely a small oversight somewhere and it was all over in seconds.