Until the advent of fossil fuel based energy slaves, the rich and powerful needed the poor and powerless to do all the hard unpleasant jobs.
In the1860s, (interestingly parallel with the growing popular elite acclaim for Darwin's and Spencer's theories of the survival of the fittest), elites began seeing that fossil-fuel 'energy slaves' were far cheaper, far more tractable and far more moral than employing human slaves.
Perhaps, said these early utilitarian proponents of the much later Aktion T4, Eastern Hunger Plan and the Holocaust, the poor need no longer be "aways with us".
But if the Nazis and their earlier ilk all around the world had succeeded in liquidating all the weak and the poor, the defective and the asocial, how then would one be able to tell - for certain - that the healthy and the wealthy were truly so ?
For, to give but one example, the idea of 'the wealthy' can be easily shown to be a relative term, not an absolute term.
A working class European family of this the early 21st century is far far wealthier, in terms of access to (energy) slaves, money and sheer comfort, than any of the top nobility families of the 13th century.
They only seem poor, only feel poor, when they compare themselves to the families of today's top 1%.
Similarly, the most advanced human civilizations circa 1940 had so many visible shortfalls from what their members hoped and thought they were capable of, that people at this imagined top could only console themselves by saying "at least we are more civilized than X, Y, or Z" down at the bottom tiers of Life.
X, Y and Z being perhaps Australian aboriginals, slime molds and the anthrax bacteria.
Civilized and advanced are relational concepts and only make sense when matched in opposing symmetry with the uncivilized and primitive.
Destroy the bottom and where then is the top ?
But as it happens, the Nazis and other Social Darwinists never got that far.
Instead Progress's symmetry of an advanced top and a backward bottom simply collapsed when assailed from top and bottom.
In WWII, the top proved to have so many moral failings (mass bombing and gassing of the innocent) at a time when the bottom proved to have so many technical advantages (natural penicillin from the penicillium slime) that the delicate balance of the symmetry of opposites couldn't hold anymore.
So, today, it is a commonplace to say that this planet was made and sustained for the tens of thousands of ancient species of microbe and the relatively recent and single human species is but a short term parasite "just visiting" planet Earth ---- a commonplace unlike to be uttered or believed in 1940 .....