Friedrich Nietzsche famously stated that “Christianity is Platonism for the masses” in his introduction to Beyond Good and Evil. His reason for giving Christianity this label was because of Christian obsession with the supreme Good talked about in Plato. This was Augustine’s summum bonum.
Nietzsche rejected Plato and other introspection orientated philosophy. It was in this context he made his famous remark:
Let us not be ungrateful to it, although it must certainly be confessed that the worst, the most tiresome, and the most dangerous of errors hitherto has been a dogmatist error–namely, Plato’s invention of Pure Spirit and the Good in Itself. But now when it has been surmounted, when Europe, rid of this nightmare, can again draw breath freely and at least enjoy a healthier–sleep, we, WHOSE DUTY IS WAKEFULNESS ITSELF, are the heirs of all the strength which the struggle against this error has fostered. It amounted to the very inversion of truth, and the denial of the PERSPECTIVE–the fundamental condition–of life, to speak of Spirit and the Good as Plato spoke of them… But the struggle against Plato, or–to speak plainer, and for the “people”–the struggle against the ecclesiastical oppression of millenniums of Christianity (FOR CHRISITIANITY IS PLATONISM FOR THE “PEOPLE”), produced in Europe a magnificent tension of soul, such as had not existed anywhere previously; with such a tensely strained bow one can now aim at the furthest goals.
Although Nietzsche was a nihilist, he correctly saw modern Christianity as an infantile version of Platonism.
reality is not optional 
I honestly didn’t understand any of what was just quoted, and it always amazes me that people will continue to quote a madman that they know ended his days literally insane. Its as if quotations are more profound to people the more insane their author, or the more incomprehensible they are due to their being nothing but drivel.
So Plotinus saw god as perfect perfection, meaning god could not change, was perfectly simple, and represented a ideal form. Augustine embraced this view. The natural “attributes of God” that this suggests are the common ones heard in the Church “omnipotence, omnipresence, omniscience, immutability, etc.” Nietzsche, a very stupid man (as you pointed out), correctly saw that modern Christianity was just the brain child of Augustinian Christianity. That is a good term for it.
Nietzsche was not a nihilist, but was actually greatly concerned with its increased dominance in our way of thinking. In the decline of Christianity in the west, we see a decrease in the State and Church’s ability to provide a seemingly universal value system to organize us; we are left with a population that all out rejects any notion of truth or value system, which is Nihilism. In this way, Nietzsche saw a direct relationship between Platonism, Christianity, and Nihilist decadence of our times. The death of god was not a celebratory act, but one that concerned Nietzsche as our inherited thought systems have left us alienated from ourselves and from the world, unable to find new guiding principles. We see this best exemplified in Late Capitalist pseudo-religion of individualist gain and pleasure. Here’s a decent starting point on the topic https://en.wikipedia.org/wiki/Nihilism#Nietzsche I highly recomend Deleuze’s Nietzsche and Philosophy, like Nietzsche, it is a highly subtle text and requires great patience and context. In Nietzsche’s thought and those similar (Heraclitus, Spinoza, Deleuze), we see a worldly understanding of god that is immanently connected to us (rather than Plato’s transcendental divinity). there I find an infinite fount of comfort and inspiration. god bless.
Modern Christianity is certainly influenced by Platonism but it cannot be called its child, at least not to the full extent of the word.
There is more to Nietzsche than meets the eye. He is one of the first great writers to confront the fact that Jesus Christ was losing his grip on us after 2,000 years. G.K. Chesterton later explained it The problem was not that people would believe in nothing – but that they will believe in anything – socialism in particular, plus all kinds of other useless ‘modern’ philosophies. Nietzsche believed that Christianity’s over-emphasis on platonic reason was an obstacle to human progress and that a metamorphosis of the gods needed to take place – I think that is happening – for example, Jordan Peterson interprets the scriptures from a mythological perspective – he makes them relevant to young people who think of themselves as secular but are nevertheless very susceptible to mythical stories – this illustrates exactly what Nietzsche was saying – if you re-present the gospels as dream-like mythological fantasies you engage us far more easily than appealing to cold, hard reason alone. Nietzsche believed in going back to pre-platonic Ancient Greece where the tragedy of life was a more prominent theme. Someone needs to write a nietzchian version of the bible – in the style of greek mythology which people can relate to emotionally. that would be useful.
It is Kierkegaard who does exactly this—putting the message of the New Testament, and by retroactive interpretation the OT too, in mythologico-tragic images. The prime example being Abraham’s near sacrifice of Isaac.