Because he is wrong, thats why.
How am I wrong? we all saw the movie and a lot of my friends have had the same questions about that particular storyline.
Okay, wrong was the wrong word, but I think that you are misinterpreting disinformation spread along during a crisis, which happens ALL the time and claiming them as failures on the Vulcans part. These movies detractors think they are plot holes...I guess I should say, they are wrong.
Right. They aren't plot holes because they can be explained within the context of the story.
I would add that no one knows what Nero is really doing until Chekov figures it out. Before that, it would probably be hard for anyone to believe Nero alone could (or would) destroy an entire planet.
I'd also add that if one were on Vulcan at the time Nero started his drill, it would probably take a while for it to sink in that this
one beam (they'd probably think the drill itself is the weapon) is causing the havoc. It would also take a while to try to figure out
why the beam is being fired. The beam was creating natural disasters on the planet. So, is this "weapon" a way of disabling Vulcan civilzation so it's incapable of dealing with an invasion? Is Vulcan being conquered? The beam itself would not destroy the planet.
As the events unfolded, they certainly wouldn't know that the beam is only a drill, and was
only used to create a means by which the
real weapon could be delivered.
They may have thought their
civilization was doomed, but not the entire planet. And even if they finally concluded that someone really was committing genocide and the population had to escape, then they certainly wouldn't have thought the entire planet would be consumed in a matter of seconds.