According to Heidegger, metaphysics started with Plato who interpreted Being as an idea. Nietzsche was the last in this metaphysical history and he brought it to an end. Nietzsche asked “what does nihilism mean?”; and he answered “that the uppermost values devaluate themselves.” Moreover, he stated that “the aim is lacking; the 'why?' receives no answer.”
Thinking within the Greek distinction of Being/Becoming (as permanent/unstable), in order to promote values that preserve/enhance life, and as an attempt to overcome nihilism through will - Nietzsche proposed: “to stamp Becoming with the character of Being – that is the supreme will to power”. Eternal recurrence of the same is to Nietzsche this constant permanentizing of the unstable. Moreover, Nietzsche's metaphysics of will to power re-interprets all the fundamental metaphysical positions that precede it in the light of valuative thought. As such, this devaluation/valuation metaphysical process is not just one historical event among the others, but is the fundamental event of Western history.
The devaluation of the highest values makes the world seem valueless. The values are gone, but beings as a whole remain. Beings possess objective actuality, overshadow and no longer need their Being, and the Being collapses into oblivion. When metaphysics asks “what is the being as such?”, since the question is addressed to the being and not to the Being, the answer is already implied in the question: being as such exists with respect to essentia and existentia. That is, metaphysics is inherently theology (as the quest for the first causes, essence, or will to power) and ontology (existence, permanence, or the eternal occurrence of the same). According to Heidegger, Nietzsche's “God is dead” is nothing more than inverted theology and ontology; that is, still proper theology and ontology.
Nietzsche carries out to the most extreme consequences other essential decisions from the history of metaphysics: the subjectivism is brought to completion by making the body the guideline in interpreting of the world, the Cartesian certitude and truth are established by transforming and securing beings in their perfectly disposability and malleability, the Greek distinction Being/Becoming (true/apparent) is inverted as the selfsame of eternal recurrence of the same and will to power, the Platonic idea is replaced by the “revaluation of all values”, and so on.
In order to provide an answer to the above “why?” of nihilism, Heidegger reminds us that: nihilism started with Plato and with the beginning of metaphysics when these values were posed in the first place, that metaphysics is not a human invention, that metaphysics can only think being and that Being itself must necessarily remain unthought, that according to metaphysics there is nothing to Being itself, and so on. As such, there is a more fundamental nihilism here at work when compared with Nietzsche's nihilism; that is metaphysics as metaphysics is nihilism proper.
According to Heidegger we must overcome our compulsion to lay our hands on everything, understand that our struggle to master beings means nothing more than to interpret them metaphysically without being able to understand their essence, that we no longer perceive the confrontation between the power over beings and the truth of Being, that in the age of fulfilled metaphysics we hardly encounters in thought what is simple, and so on. In order to overcome this destitution, there is a need to experience our need for Being. However, since it is more essential and older, the destiny of Being is less familiar to us than the lack of God – God that Nietzsche declared dead with such insight and joy.