The most precious knowledge is revelation knowledge. It provides both foundation and direction.
The Greek philosophers were honest but devoid of revelation knowledge. So, their exercises in logic and reason brought no satisfaction.
When revelation knowledge came, philosophy was seen for what it was - mental gymnastics that were interesting but empty and inferior.
Unfortunately, modern philosophers having had access to revelation knowledge, rejected it. This is both sad and unnecessary.
Insanity is the 'normal' product of intellectual pursuit of understanding without revelation knowledge. This is because that which is really precious about existence is spiritual, not physical. Spiritual knowledge comes by revelation. It elevates humanity and connects them with their Creator. That connection centers us so that all other things may be understood from a stable position.
Not picking on Nietzsche (since the same could be said of other philosophers) but he made no positive contribution to the human condition. When you spend your life searching for truth and only come up with vagaries, incongruances and emptiness, you go insane.
That's why there is no substitute for revelation knowledge.
The Creator manifested Himself in flesh and blood to reveal Truth to humanity. His name is Jesus - the way, the Truth and the life.
The most important Truth that Christ revealed is that He loves us, has forgiven us and wants an eternal relationship with us.
I am not an accident. The universe was created for a purpose. There is a plan in place. The loving Creator wants every person to receive that revelation knowledge.
Nietzche falls into insanity - Wikipedia:
On 3 January 1889, Nietzsche suffered a mental breakdown. Two policemen approached him after he caused a public disturbance in the streets of Turin. What happened remains unknown, but an often-repeated tale from shortly after his death states that Nietzsche witnessed the flogging of a horse at the other end of the Piazza Carlo Alberto, ran to the horse, threw his arms around its neck to protect it, then collapsed to the ground.
In the following few days, Nietzsche sent short writings—known as the Wahnzettel ("Madness Letters")—to a number of friends including Cosima Wagner and Jacob Burckhardt. Most of them were signed "Dionysus", though some were also signed "der Gekreuzigte" meaning "the crucified one". To his former colleague Burckhardt, Nietzsche wrote:
'I have had Caiaphas put in fetters. Also, last year I was crucified by the German doctors in a very drawn-out manner. Wilhelm, Bismarck, and all anti-Semites abolished.'
Additionally, he commanded the German emperor to go to Rome to be shot and summoned the European powers to take military action against Germany, that the pope should be put in jail and that he, Nietzsche, created the world and was in the process of having all anti-Semites shot dead.