Simply put, God's original plan, and the very reason He created humans. We are to image Him (just like the angels) according to the way He created us, a little lower than them. Also, keep in mind Jesus is our creator.
"And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth." (Genesis 1:26)
Then the fallen angels came and were destroying humans and the earth and henceforth the flood during the time of Noah. The war between good and evil has been raging ever since. When the 2nd advent occurs, then Jesus will restore all things back to what they were before the fall of the "first Adam."