As to why he embraced Fusion, I’ve also read he was financially motivated but at the same time, genuinely enjoyed the music of of Hendrix and Sly. Plus, he was creatively restless; it was only natural that he would not stay in one place for long. And it’s worth recognizing that he worked his way into it; it wasn’t a single, sudden leap from "If I Were A Bell" to "Miles Runs the Voodoo Down".
Yes, you and @wharfy are correct as to the motivation guiding Miles' transition into different jazz genres. I read his autobiography when written in the late 1980s. Creative urges, wanting to remain current and increasing his income status were major factors that he openly acknowledged. He was a big admirer of Prince in that era.
I respect all of Miles' work but have to say that his earlier era of late 1940s to the early 1960s (Bebop-Modal) are what I enjoy most. Certainly to each their own.
Charles