That is a possibility, but how? Was it a vision? did God whisper in his ear? Did Moses having a deep yearning to write about creation, and Genesis is that result? Any and all can be true. We just don't know.
We just don't know."
Yes we do.
"Above all, you must understand that no prophecy of Scripture came about by the prophet's own interpretation. For prophecy never had its origin in the will of man, but men spoke from God as they were carried along by the Holy Spirit." (II Peter 1:21)