They're trying to dumb-down the fanbase for things like science fiction. It's fiendish, really--they're doing it by long-range FTL information transmission, since the journey itself is slow. They realized back in the Fifties that people who read science fiction and fantasy would be particularly able to detect their nearness, simply because they've bene reading and thinking so much about things that are a bit Other to us. So they decided that the best way to invade and take over would be to make it so that we'd never expect them, and they could come in slowly. They're doing this by tainting the pool of writing that new readers of science fiction and fantasy fanfic can access. This disgusts the readers, causing no small few of them to leave the fandom entirely out of shock. This cuts down the fanbase, which cuts down the number of people willing or even able to think about anything other than what they see everyday, which means that when the Others finally arrive here, in another thousand years or so, we're going to be in trouble. It's genetic manipulation through the obstruction of information! Controlled evolution. They're readying us for a hostile takeover.
That's what I think, anyway. In my head.