Mozart

what historical developments led to this image we have of Mozart being the absolute musical genius?

How unique were his capabillities and his personality? Are there any simmilar figures outside of the western world?

1.) His music is very intricate, complex and yet beautiful.
2.) His abilities were very unique. He was a prodigy as a child. His personality was very autistic though and he used to prance around rooms and do other bizzare things.
3.) There are composers outside of Europe but that's a vague question.

3) talking about composers with a similar status in pop culture / who were famous for being a child prodigy

Justin bieber

He's a unique polymath even within the field of classical music.
Take Beethoven or Bach as his closest rivals. Everything they can do, Mozart can do. Also Mozart can do stuff neither were capable of (e.g. comic opera, dance music)
And Mozart composed as prolifically as those two despite dying young.

The most similar figure is Shakespeare. Nobody else has written as many classic plays (Shakespeare has maybe twenty masterpieces, nobody else come close). Other playwrights can excel in tragedy or comedy, but nobody could do both. Ibsen or Chekhov could never have written Twelfth Night or AMND. Oscar Wilde could not have written King Lear. But Shakespeare could have written anything by those writers.

Outside the west there isn't the same system of notation, so music is orally transmitted and never gets as sophisticated as western art music (not saying it's lower quality, just less sophisticated)

Sorabji was kind of famous from a youngish age I guess. There really isn't a close non-Euro comparison.

Papageno is Mozart's best character.

Mozart a genius?

Even average contemporary musicians like Kanye are fairly superior technically from an objective standpoint, lelt alone the really good contemporary ones, Mozart is overrated because he's very old but at the end of the day he was just an average joe who got forced to play music from a young age, nothing special, interesting from an historical standpoint, but boring now that we have much better.

Have to work harder for a (you) I'm afraid

there are similar figures IN the western world, its just they weren't as good. Mozart didn't represent much of a shift in musical style, he was just a master of the style of his era. For a hundred years you couldn't listen to a symphony or two without hearing a Mozartian theme, pastiche, or clone.
He was known for having the "perfect" amount of notes in order to convey an idea, he was known for his rigid yet beautiful use of standard musical formatting (such as sonata form and ABA, I IV V, etc). During his day he was also known as a prodigy as a musician (as many composers) he was one of the best pianists in Vienna and had a very unique style and interpretation (though still very rigid, it was said to be unique in its perfection).