I know this post is long, was trying to be as thorough as possible, but there seems to be layers to this and it's probably better to allow others to add to the discussion.
My theory is God (being omniscient), knew before he created everything, what was going to happen with some of his created beings, and so his masterplan was to display his glory (his ultimate power and authority) through his creation? It seems this way to me after delving into the scriptures. What say you?
Let's start with the fact that God is all-knowing:
What does it mean that God is omniscient?
"Omniscience is defined as “the state of having total knowledge, the quality of knowing everything.” For God to be sovereign over His creation of all things, whether visible or invisible, He has to be all-knowing."
Hebrews 4:13
13 Nothing in all creation is hidden from God. Everything is naked and exposed before his eyes, and he is the one to whom we are accountable.
Jeremiah 23:24
24 Can anyone hide from me in a secret place?
Am I not everywhere in all the heavens and earth?”
says the Lord.
Isaiah 46:9-10
9 Remember the things I have done in the past.
For I alone am God!
I am God, and there is none like me.
10 Only I can tell you the future
before it even happens.
Everything I plan will come to pass,
for I do whatever I wish.
Before God created everything (and us) he already had a plan on how he would ultimately display his glory:
1 Peter 1:19-20
19 It was the precious blood of Christ, the sinless, spotless
Lamb of God. 20 God chose him as your ransom
long before the world began, but now in these last days he has been revealed for your sake.
Revelation 13:8
8 And all the people who belong to this world worshiped the beast. They are the ones whose names were not written in the Book of Life that belongs to
the Lamb who was slaughtered before the world was made.[a]
God (the Father) created the world through the Son (the lamb/the word/Jesus Christ):
Colossians 1:16-17
16 for
through him God created everything
in the
heavenly realms and on earth.
He made the things we can see
and the things we can’t see—
such as thrones, kingdoms, rulers,
and authorities in the unseen world.
Everything was created
through him and for him.
17 He existed before anything else,
and he holds all creation together.
Note: the "authorities" in the unseen world (See video below)
God created human beings in his image to reign over creation on the Earth:
Genesis 1:26-28
26 Then God said, “Let us make human beings[a] in our image, to be like us. They will reign over the fish in the sea, the birds in the sky, the livestock, all the wild animals on the earth, and the small animals that scurry along the ground.”
27 So God created human beings[c] in his own image.
In the image of God he created them;
male and female he created them.
28 Then God blessed them and said, “Be fruitful and multiply. Fill the earth and govern it. Reign over the fish in the sea, the birds in the sky, and all the animals that scurry along the ground.”
Then the temptation and fall: (my theory is that because satan was an arch angel, and part of the divine council, perhaps this temptation was agreed upon?) But only God knew what the outcome would be. I also never thought of this before, but the serpent knows about good and evil. (Or, knows of it?)
Genesis 3:1-5
The Man and Woman Sin
3 The serpent was the shrewdest of all the wild animals the Lord God had made. One day he asked the woman, “Did God really say you must not eat the fruit from any of the trees in the garden?”
2 “Of course we may eat fruit from the trees in the garden,” the woman replied. 3 “It’s only the fruit from the tree in the middle of the garden that we are not allowed to eat. God said, ‘You must not eat it or even touch it; if you do, you will die.’”
4 “You won’t die!” the serpent replied to the woman. 5 “God knows that your eyes will be opened as soon as you eat it, and you will be like God, knowing both good and evil.”
An example here that anyone hiding from God, and him not "knowing" what happened is impossible, as he is omniscient:
Genesis 3:8-11
8 When the cool evening breezes were blowing, the man[a] and his wife heard the Lord God walking about in the garden. So they hid from the Lord God among the trees. 9 Then the Lord God called to the man, “Where are you?”
10 He replied, “I heard you walking in the garden, so I hid. I was afraid because I was naked.”
11 “Who told you that you were naked?” the Lord God asked. “Have you eaten from the tree whose fruit I commanded you not to eat?
In certain parts of scripture, God seems to give satan a certain amount of leeway, but he seems to have lost his position in how God curses him:
Genesis 3:14-15
14 Then the Lord God said to the serpent,
“Because you have done this, you are cursed
more than all animals, domestic and wild.
You will crawl on your belly,
groveling in the dust as long as you live.
15 And I will cause hostility between you and the woman,
and between your offspring and her offspring.
He will strike[a] your head,
and you will strike his heel.”
He hasn't been cast to earth after the fall of humanity as he's still able to interact with God, and even suggest more temptation, so he must still be part of the divine council, but in a lowly position:
Job 1:6-12
Job’s First Test
6 One day the members of the heavenly court[a] came to present themselves before the Lord, and the Accuser, Satan, came with them. 7 “Where have you come from?” the Lord asked Satan.
Satan answered the Lord, “I have been patrolling the earth, watching everything that’s going on.”
8 Then the Lord asked Satan, “Have you noticed my servant Job? He is the finest man in all the earth. He is blameless—a man of complete integrity. He fears God and stays away from evil.”
9 Satan replied to the Lord, “Yes, but Job has good reason to fear God. 10 You have always put a wall of protection around him and his home and his property. You have made him prosper in everything he does. Look how rich he is! 11 But reach out and take away everything he has, and he will surely curse you to your face!”
12 “All right, you may test him,” the Lord said to Satan. “Do whatever you want with everything he possesses, but don’t harm him physically.” So Satan left the Lord’s presence.
Zechariah 3:1-2
Cleansing for the High Priest
3 Then the angel showed me Jeshua[a] the high priest standing before the angel of the Lord. The Accuser, Satan, was there at the angel’s right hand, making accusations against Jeshua. 2 And the Lord said to Satan, “I, the Lord, reject your accusations, Satan. Yes, the Lord, who has chosen Jerusalem, rebukes you. This man is like a burning stick that has been snatched from the fire.”
So, when was the adversary cast to earth?
How, why, and when did Satan fall from heaven?
I'm thinking by the time he knew about Jesus:
Revelation 12:13
13 When the dragon realized that he had been thrown down to the earth, he pursued the woman who had given birth to the male child.
So where do we fit in as the fallen creation?
Ephesians 3:10-11
10 God’s purpose in all this was to use the church to display his wisdom in its rich variety to all the unseen rulers and authorities in the heavenly places. 11 This was his eternal plan, which he carried out through Christ Jesus our Lord.
The key word that we find throughout scripture, is glory.
John 17:1-5
The Prayer of Jesus
17 After saying all these things, Jesus looked up to heaven and said, “Father, the hour has come. Glorify your Son so he can give glory back to you. 2 For you have given him authority over everyone. He gives eternal life to each one you have given him. 3 And this is the way to have eternal life—to know you, the only true God, and Jesus Christ, the one you sent to earth. 4 I brought glory to you here on earth by completing the work you gave me to do. 5 Now, Father, bring me into the glory we shared before the world began.
What is God's "glory"?
"In Exodus 16:7 we read "and in the morning you shall see the glory of the LORD" (RSV). What is the "glory" of YHWH? First we must recognize that the "glory" is something that will be seen. Secondly, the word "glory" is an abstract word. If we look at how this word is paralleled with other words in poetical passages of the Bible, we can discover the original concrete meaning of this word. In Psalm 3:3 the kavod of Elohiym (God) is paralleled with his "shield" and in Job 29:20, Job's kavod is paralleled with his "bow." In Psalm 24:8 we read "who is this king of the kavod, YHWH is strong and mighty, YHWH is mighty in battle." The original concrete meaning of kavod is battle armaments. The meaning "armament" fits with the literal meaning of the root of kavod, which is "heavy," and armaments are the heavy weapons and defenses of battle. In the Exodus 16:7, Israel will "see" the "armament" of YHWH, the one who has done battle for them with the Egyptians."
SOURCE
So essentially, we're part of a spiritual battle:
Ephesians 6:12
12 For we[a] are not fighting against flesh-and-blood enemies, but against evil rulers and authorities of the unseen world, against mighty powers in this dark world, and against evil spirits in the heavenly places.
13 Therefore, put on every piece of God’s armor so you will be able to resist the enemy in the time of evil. Then after the battle you will still be standing firm.
2 Corinthians 3:18
18 So all of us who have had that veil removed can see and reflect the glory of the Lord. And the Lord—who is the Spirit—makes us more and more like him as we are changed into his glorious image.