It took only one. The man who sold us out.
It was 41 in the new calendar and things were still bad, yet no one could remember when they were better.
Just like in your time, science's laboratories were producing ever greater wonders, fixes and problems. And all that data that they produced; all those drugs that affect us, and how; and all the little fiddly bits of DNA and how it's basically the blueprint for life on Earth; they published it all, except for things like when the Tobacco companies hid that their products cause cancer.
They were headed towards us, when we detected the aliens, about as far away as the sun. They set up their base in the center of the face of the moon.
And they took all that scientific data, and one person to translate it, and they made something, something like a disease, which makes us docile, and their slaves.