I think the idea that Miles changed jazz is a bit of a generalized statement. Many people credit him with a lot of the success. In a lot of cases, Miles was the name on the marquee. In a lot of cases Miles was a member of a group of musicians who had like minds and his name was the strongest, with the biggest reputation.
Miles was indeed a visionary, a great horn player, a melodic improviser and a great composer. Miles got in with Bird and that clearly to me is the launching point. Here was this kid that Bird brought in, and bam instant credibility.
The Cool jazz thing was Miles' colaberations with Gil Evans and that crew of people.
Kind of Blue was his colaberations with Bill Evans, his interest in impressionistic music and Gil Evans' influence on him.
The 60's quintet was I would say more a result of his band members then himself. Wayne wrote a lot of that music and that rhythm section was beyond special.
Miles never really did anything totally new all by himself. He was able to surround himself always with great young players and as a group, they were innovative many times. I think the Electric period was very much a Miles Davis thing, where he purposfully wanted to push the music forward radically.
imo at least