>>It was called fusion - later smooth jazz and it’s Father was Miles Davis.
Miles certainly was in the nexus where rock fusion was born - but the key element in fusion, and jazz, and blues.. is the improvisational freedom in the context of a group of mutually supportive, but individual, musicians.
The history of improvisation preceded Miles:
http://scaruffi.com/history/jazz1.html
To me, the significance of “So What” is in the relative simplicity in form that it represents when compared to the preceding bebop era - which was characterized by more changes, with more notes, with more complexity... for what?
So What demonstrated the essence of what jazz could be without all that pretentiousness.
"Reach up while reaching down,
Grow while helping others"
https://www.youtube.com/watch?v=EPFXC3q1tTg&feature=youtu.be&t=30m52s
Although Miles most always chose the minimalist approach,
I highly doubt that he considered all bop reharmonization pretentious.
Certainly Miles respected everything that Monk, Bud and Bird contributed.
Miles was mentored by Bird. The interviews I have seen reflect the reverence of the student to jazz master relationship.
“So What” reaches the highest levels not only because of the modal approach but also because of the rhythm and phrasing wrapped up in what I would call the “perfectionist approach”.
These fellows were not messing around - anybody can play modally. Although they were introducing the style. They were also playing at the top of their game... highly focused as well as spiritually connected and devoted to making music
Miles - John Coltrane - Bill Evans - Cannonball Adderly - Paul Chambers - Philly Joe Jones...
My goodness and man alive... ha ha ha
And in the end of it all So What