And the good guys only succeed because of stupid mistakes the bad guys make.
No, the good guys do not succeed at all. If you watch it critically, it becomes obvious that the humans are the villains and the aliens are the good guys.
Earth sends a message asking the aliens to come. And when they show up a bunch of super-jingoistic military goons shoot at them without provocation. Of course they attempted to defend themselves. And throughout it all, the aliens always acted far more humanely than their human counterparts, attempting to minimize the loss of life even as they were being slaughtered.
This isn't a case of Hirogen wannabes invading. This is a case of the military royally screwing up a first contact that could have been and should have been peaceful.
And blowing up the NASA array was almost certainly futile and counter-productive. When the aliens send a search and rescue group to find out what happened to their scouts, they're going to be incredibly pissed off at humanity.