I think there's a huge difference between what the public thinks creativity is, and what artists think it is.
The public tends towards thinking that new music just sort of magically occurs when a unique individual comes along. Musicians understand the incremental evolution, all the borrowing, and the derivative nature of what feels fresh and new.
Of course, once in a blue moon, someone comes along who just seems like they flew in from Mars or someplace. Like Hendrix seemed in 1967 or thereabouts. Actually, I do think Thelonius Monk did actually fly in from Mars
Debussy made just an incredible leap in what he did with late Romantic/Early Modern music.
I'm not sure there's much accounting for types like the ones cited above.
But for a more garden-variety explanation of musical evolution, it seems to me so often is that it's cross-pollination of prior genres. Like Ray Charles basically lifting black church music and singing about "This Little Girl of Mine" instead of "This Little Light of Mine."
But you can't, or at least I can't, just start mixing up stuff from genres, throwing in just whatever sounds different for the sake of difference, and come up with anything but garbage. But I can - just sometimes - hear how something from, say, Debussy, could easily translate into an EDM track. Or if you took the guitar sounds from Dr. Robert and made something like Terry Riley's "In C" from it, that just might work.
The people I know who do really ingenius and new-sounding things almost all put a lot of work into it, while at the same time, what they come up with seems, to them, to just obviously work. Even if no one else thinks so - at least at first.
There's a little vignette from the movie "Echo In the Canyon" (it's on Netflix now) where Roger McGuinn describes how he had this idea of merging folk with a beat like he heard in a Beach Boys song. He tried it out as a solo singer-songwriter in some L.A. clubs, but the folkie crowd absolutely did not go for it. But to him, he heard it, he knew it would work, so he persisted until he hooked up with other guys that could also hear how it worked, and viola, The Byrds were born. Folk-rock, a baby genre.