It's a test committed by the Federal Bureau of Investigation in the efforts to understand the mentality of the Japanophiles, Weeaboos and Touhou culture enthusiasts. The purposes of said experiment is to find out whether or not these individuals pose any legitimate threat to the outside world. On day two, the FBI decided to close off their investigation; ruling that such individuals, for a fact, do not post a large threat to major populaces, but only a large threat to themselves. The FBI wanted to shut down the island, but couldn't successfully get any agents unable to look at the forum and get depressed, vomit, or have Futaba bully them until they psyche's cracks. So, they left it running as an abandoned experiment.
Welcome to Anime Princess Island! Enjoy your stay princess~!