"And for some reason, it wasnt applied to humans until Darwin's time, then Hitler's."
/facepalm
Except it was: Plato discussed such a concept 400 BCE to make a guardian class of protectors, an idea put into practice by the Spartans (who practiced a brutal form of survival of the fittest selective breeding). It was practiced by countless royal lines across Europe through out history on the basis of the flawed concept of "royal blood lines" among humans (with disastrous results).
THIS is why your statement is both malformed (in that you are making incorrect assumptions about history) & also irrelevant to this discussion.
As for why it became popular in the late 1800's & early 1900's is simply because the naturalist mechanism was accurately explained for the first time.
At which point the British
Eugenics Education Society and the
American Eugenics Society were created. Both sought & received support from leading clergymen, and modified their message to meet religious ideals. (Citation in case you are interested in doing some actual reading
shm.oxfordjournals.org/content… )
"Just quit the "atheism vs christianity" fake dichotomy"
There is no "Atheism vs Christianity" in this conversation: There is just your misunderstanding of history & the facts that demonstrate your misunderstanding of history.