Among all the things to be created, man presented the greatest challenge to God, since uniting the rational spirit to matter would, by the fact of the finitude and peculiarities of both, be naturally corruptible.
To make sense of Genesis, we may as well imagine the Garden of Eden to have been located not in this world but in the literal highest heaven / paradise. God created Adam as well as He could, but He foreknew it would not be enough. The human nature is unstable and tended toward self-destruction even in the world free from most of the burdens of the flesh, the world, and the devil.
Therefore in this world we are tasked, by being forced to contend with the forces of evil, with creating a second nature that would support and preserve the first.
The first nature was divinely created but inadequate; the second nature obtained by strict obedience to natural law and to grace besides despite tremendous obstacles will be enough even for the entirely of our future everlasting lives, but it could not have been created by God, arising as a result of our own living and striving.
The human nature as an idea is well-defined; there are no bugs in natural law.
God and man therefore come together in the order of nature in the middle, with God creating the ideal that only heroic human effort could possibly reach and maintain.
The human project is made even more ambitious by grace, but that’s a story for another time.