Like Rivvon and Don said, not warning the public about this restriction sooner was a poor move from the company, in what is Pokemon's 20th anniversary year nonetheless, about not leaving a warning that the venue is so small that it's causing space concerns. The event will be streamed, but that's not enough to stop the sour taste left in the mouths of those who were planning to go the event to spectate. The restricted size also made sense in why there was no local wi-fi event Pokemon announced, in what is meant to be the final Worlds event before the move into 7th Gen.
Hopefully the company will learn from this and have a much more sizable location booked for the 2017 Worlds event.