Hitler believed in selective breeding, not natural selection. They're not the same thing.
And selective breeding was around long before Darwin.
You are correct. They are not the same thing. It's a worthy distinction too.
Hitler had an image of what the human race "supremely" should look like. He used deviant methods to form and shape the world into his image.
That's how a cult operates, in this case a white supremicist arian cult.
Since Hitler considered the arian race to be supreme he incorrectly applied the selection ideology, a Darwinian twist to justify his evil deeds.