How did Moses write the events which happened ~2000 years before him?

Except the book of Genesis, I believe that it is possible to make some plausible possibilities on how the books of the Bible were written. Moses wrote about himself, Joshua recorded his conquest of Canaan, some priests or prophets recorded the stories of Gideon, Samson and Ruth. Samuel recorded the events in his lifetime, historians recorded the chronicles of the kings of Israel, prophets wrote down their visions and messages from God, the apostles recorded the life of Jesus, apostles wrote letters and John wrote down his visions. Now, I can't make any hypothesis how Moses could write down the stories which were around 2000 years before him. The Creation story where no one was there to witness is the most astounding account. Genesis contains many complicated contents such as the years of the first men, thousands of names, complicated family trees, detail stories of people and such. How have historians and theologians explained how Moses wrote the Book of Genesis?