Hitler (1945-03-19, as quoted by Albert Speer in *Inside the Third Reich*, 1970, Macmillan, p. 440):

> For the nation has proved to be the weaker, and the future belongs solely to the stronger eastern nation. ([Google Books][1]—may be paywalled.)

Hitler (1945-04-29, as quoted by Traudl Junge in *Until the Final Hour*, 2005, Phoenix, [p. 175](https://archive.org/details/untilfinalhourhi0000jung_q7f2/page/174/mode/2up?q=%22germany+is+lost%22)):

> Germany is lost. It was probably never mature and strong enough for the task I intended it to perform.

In Hitler's crude and mystical Darwinist survival-of-the-fittest world-view, Nature decrees that stronger races/peoples defeat weaker ones.

The Germans lost simply because they were weak while the Russians/Slavs were strong. That was the fundamental reason and all else were mere unimportant details.

  [1]: https://books.google.com/books?id=lt4ZPz8n53cC&q=%22the%20nation%20has%20proved%20to%20be%20weak,%20and%20the%20future%20belongs%20entirely%20to%20the%20strong%20people%20of%20the%20East.%22