Why is the hero of Dostoevsky's novel 'The Idiot' Prince Myshkin — an idiot?

Why do they call Prince Myshkin an Idiot?
The name of Dostoevsky’s novel has many layers.
The idiot may refer to not only an intellectually disabled person. It was also used to refer to people who lived differently, did not follow the rules of society.
Myshkin finds himself in the heart of the St.Petersburg high society.
He seeks to help everyone, save them.
The author paints his protagonist as a positively beautiful person, somewhat resembling Jesus.
He contemplates what would have happened if we had met Myshkin.
Some people mock Myshkin, others see him as a prophet.
But all of them unanimously decline his help. And by doing that drive him insane.
Another meaning of the word Idiot is a holy fool, touched by God.
In Christianity, such people are believed to be the channel of God’s love for humankind.
Myshkin bears that Christian kindness and love. He shares his light with his loved ones.
He dedicated his life to serving others, but doing that made his life a tragedy.
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[dixztube]

i really really enjoyed this - gonna get through dostoe's other works