What Will The Neighbours Think?

By which I mean our interplanetary neighbours.
They will visit Earth in 50 years and find nothing but ruins. There will be no corpses. Nearly all the people will have marched dutifully to the extermination camps to "save the planet".

There won't be many people left; a few cave dwellers perhaps, more likely no people at all.
What will the visitors conclude?
They will examine the ruins and find that the world of Humans was destroyed by a fraud; it will be destroyed by the mixture of trust and lies, the poison that allows and ultimately creates all holocausts.
They will look at the mid twentieth century and see the monomental effort of moral expression that stopped the Nazis; the dogged determination that saw to it that the Soviet Union also collapsed, and they will conclude that the real perpetrators of these monstrosities were merely toying with the humans.
The humans failed to identify them and their evil accurately enough or often enough, and like the infinitely patient game-players they undoubtedly were, they just swallowed every truth, took every setback in their stride and put an arm around humanity's shoulder and led the dazed, tiring population from one illusion to the next, pausing to reveal themselves and their evil hatred only when some human of stature resisted too well.

At this stage, they could be seen. But the watchdogs of humanity were too incompetent to bark. Like dogs miaowing, they merely snorted and went back to somnolent staring, allowing the evildoers to manage yet another fait accomplit.
And around 2020, when it was found that there were just too many people, found by 'science', the absurdity of scientific socialism was suddenly standing before humanity, saliva dripping from its jaws, in a ruder health than it had ever been.

But this time no moral effort; the children had been destroyed in advance and made to believe that the lies were true, or that they were lies that couldn't be stopped.
Not all of us died voluntarily.
That's why there will be plenty of ruins.

The age of humanity is over.
Welcome to the new Hell.