Mozart had extensive education and training????
Thats kindergarten. You might be thinking of other composers who are regarded as his equals -- Mozarts brain was just tuned for music in a way ours are not.
I would have been composing at 5 had my father been a musician/composer/teacher! (I did start piano at 4, in a not-particularly-musical household) As it was, I remember hearing that when I was about 9, and thought "Oh well, it's too late for me" - which is a shame! But his first compositions weren't great. You write that like it's some super-human feat or something.
"he was a prodigy from the earliest age. ... Mozarts brain was just tuned for music in a way ours are not." I don't know why people talk like that. Maybe as an excuse for not achieving great things themselves, or even having to try.
There was a Hungarian guy who decided to train his 3 daughters to be chess players, to see just how good they could be given a proper training. The 2nd strongest sister became world champion. The strongest one never played in women-only events, she was too strong, and turned out to be the strongest woman chess player of all time, by a long way. (i.e. Susan and Judit Polgar) I don't think it was because their brains were 'tuned for it'. They just had the perfect environment.
If we applied the same training and familial advantage to many kids would any of them turn out like Mozart?
I'd argue they probably wouldn't because his brain was fundamentally different and that made the difference.
If he didn't have those advantages would he have been discovered as a prodigy as quickly and as early? Maybe not.
It could be that many musicians with a similar background were/are similarly as good as Mozart, and Mozart's music is especially famous for its cultural appeal and his father's aggressive "marketing" to royalty. There are many reasons one particular musician's musicical legacy can succeed aside from raw skill and creativity, much like the success of a company has a nontrivial luck component.
It could also be that he really was extraordinary above and beyond his family's musical background. Like most discussions about the nature versus nurture of genius, we can't really assert one thing or another.
I'm asking honestly, because I'm pretty sure that I'm not having a typical life experience. Personally, I don't really bother to listen to music, because music is never further away than wanting to hear a melody. It's something to do on the bus, or when my mind is otherwise unoccupied. One starts with a note or a scale, finds a 'lick' in it, develops it into a theme or refrain, introduces a counterpoint or noodles around through the keys a bit, and eventually we work around to a restatement or finale (or get bored or forgetful in the middle). I suspect that this is easier for me than others, but I don't think that I'm any kind of musical genius. I'm at least hoping that creating music is more of a normal part of the human condition than not, at any rate.