Writing Must Create Context

I’m writing a book. Or, at least, I hope to be writing a book.
A bunch of the stuff I’m working on now is thinking about who it serves, it’s purpose, it’s vision and the breakdown of the big ideas into smaller ideas that tell a story.
One thing is clear. A great deal of writing is about creating a context to learn. It’s not so much that any particular idea is the key. Because you can have many a good idea but without a good context for the reader, the idea will likely not make it thru the juggernaut of noise to be received.
So, writing is about creating context for the ideas so that the thinking can fit into some system of the reader.
This is harder than it looks.