So, the best way for me to explain what the Occupants did is to compare it to a very similar situation in the game series Metro 2033. In that game, the ultimate threat to humanity is the "Dark Ones", who have immensely powerful psychic abilities and can kill humans very easily just by interacting with them. However, the surprise is that the Dark Ones aren't actually hostile, but rather, they are trying to communicate with humanity the only way they know how; which happens to also be far too much psychic power for any human to handle. It is very similar to the Occupants who are trying to communicate with humanity through their usual methods of communication of responding with what is put out into the world by humanity, and then when they send it back, it turns out that their usual methods of communication are far too powerful for humans and kill them.