My posts in an earlier discussion about about Hitler and antisemitism give
some research sources with clues. He seems to have bought into/pandered to
a combination of pseudoscience about Eugenics, antisemitism, and a master Aryan
race, and put it together to mean inferior people should be eliminated/made
unable to reproduce to advance the Aryan race.
http://www.jehovahs-witness.net/social/current/239248/1/occasional-eccentricity-and-abnormal-attitudes-of-Jehovahs-Witnesses-in-regard-to-the-Anti-Islam-Videographere28099s-First-Amendment-Right-to-Insult-Religion-cited
Russell then JWs leaders, like Popoff, have clearly feigned exclusiveness to
pander/market to people who want exclusive religious leaders. I think Farrakhan
has as well--probably more a cynical businessman for bigots than an actual
bigot. Maybe Hitler was a pandering politician or believed his own stuff.
Ideas that are archaic now about Eugenics and racism fooled a lot of people
then--they might have fooled Hitler or he saw a market to exploit. He probably
pandered to Christians who were antisemitic with his Positive Christianity
variation, for example.
http://en.wikipedia.org/wiki/Positive_Christianity