So, as the other commentator says, evolution implies some races are "more favored" than others, i.e. superior. Outside the modern negative connotations of "racism" Darwin's title is racism in a nutshell: the claim that some races are superior to others. In turn, this doesn't mean that the "superior" races need to exploit the "inferior" races, that's an added assumption. The "superiors" could instead use their power to benefit everyone else.

This is in contrast to the common religious view point that even though some people may have more talents than others, this does not make anyone inherently superior to another in that they are more valuable and more worthy of preservation.

So, Nazis can endorse their brand of human driven evolution quite consistently with Darwin's view. However, Nazis have to twist religious doctrine to support their view.