Nazi obsession with Lebensraum was based to a very significant extent on their firm commitment to make sure that the horrors of the Blockade of Germany and of the hunger of 1917-19 never happen again. However, it was their short-term objective (and drive).
And there was also a long-term objective and drive. Nazi viewed German women as essentially breeding machines. Which would have inevitably resulted in an explosive – and permanent – population growth (that fulfilled God’s commandment stated in Genesis 1:28 – “be fruitful and multiply”).
Which – in turn – will sooner or later require physical expansion of German territories via military conquest and colonization (with inevitable cleansing of these territories of the native population).
Successful military conquest obviously required a military victory over not-always-weak opponent. And to achieve this victory in every war (and permanent territorial expansion meant essentially permanent war), Nazi Germany needed an “absolute weapon” (i.e. a weapon that will give the German Wehrmacht a decisive advantage over every opponent).
Wehrmacht did have one such weapon. The blitzkrieg – a revolutionary method of land warfare that allowed Nazi Germany to defeat and conquer Poland, France, The Netherlands, Belgium, Luxembourg, Albania, Yugoslavia, Greece, Denmark and Norway.
And – had Adolf Hitler not committed catastrophic strategic blunders – would have led to the defeat of the Soviet Union (i.e., to a successful execution of Operation Barbarossa).
However, the blitzkrieg was totally useless against the enemy protected by a wide stretch of water (i.e. Great Britain, the USA, Canada, etc.). Or even colonial British troops in North Africa as it turned out.
War with these enemies (and with the Soviet Union on the Eastern front after the failure of blitzkrieg) was inevitably a war of attrition. To win this war, totally different weapons were needed.
The purely military weapons that Nazi Germany needed to win the war on attrition and achieve world supremacy were obvious: a nuclear bomb; its carriers (intercontinental high-altitude jet bombers and later nuclear-tipped ballistic missiles) and a mighty surface-to-air missile (e.g. Enzian-class).
However, to win this war and to achieve world supremacy (and quite possibly to develop the abovementioned weapons), the Third Reich needed another powerful weapon – the Übermensch himself.
It is well-known that just about all human beings (“Menschen”) discover and realize 10% or even less of their potential – thus falling far short of self-actualization (let alone self-transcendence). And thus do not achieve genuine happiness.
An Übermensch – by definition – discovers and realizes 80-90% (i.e. just about all) of his or her productive and creative potential. Which allows him (or her) to make far better decisions and implement them in a far more efficient way than the “regular folks” can ever do.
Thus all but guaranteeing both the victory in every possible kind of war with every possible kind of component and a highly efficient management of conquered and colonized territories.
The only question is how to transform “regular Germans” into Übermenschen.