The answer to your question is that God is a perfect teacher with a perfect sense of justice.
I will illustrate and then explain: (this is a completely hypothetical situation)
Imagine that there is a flight from the US to Switzerland. The pilot is very good, in fact he is a perfect pilot. He has more knowledge and experience that anyone else in his field. Now after getting the jet into the air, one of his co-pilots decides that he can fly that plane better. He charges that the pilot doesn't know what he is doing and that he would make a better pilot. What does the pilot do? The pilot knows that he can fix any mistakes his co-pilot makes and by letting the co-pilot fly for a little while he will prove to everyone that there is no better pilot than he.
So he hands over the controls and gives the co-pilot a set amount of time to prove his accusations. The pilot sits back and watches, not wanting to help because that would just prove his co-pilot right. Well his inexperienced co-pilot is soon heading off course, in a direction that the pilot never intended. The pilot calmly sends his oldest friend and worker to tell everyone aboard the jet that everything is under control and will be fixed shortly.
Eventually the co-pilot's time runs out and the flight is way off course. He has proved himself wrong. The pilot then takes control of the jet back, as he has promised. He then makes some adjustments to steer them all in the correct direction. He lands the plane at its destination as was intended.
The pilot is God and the co-pilot is Satan. God's intention for the earth never changed, just as that aircraft's destination had not changed. Isaiah 45:18
"For this is what Jehovah says,
The Creator of the heavens, the true God,
The One who formed the earth, its Maker who firmly established it,
Who did not create it simply for nothing, but formed it to be inhabited:
“I am Jehovah, and there is no one else."
"The righteous will possess the earth, And they will live forever on it."
Satan charged that God is a liar, questioned man's motive for loving God (letting him be pilot), and sought a position higher than God's. Genesis 3:3-4
"But God has said about the fruit of the tree that is in the middle of the garden: ‘You must not eat from it, no, you must not touch it; otherwise you will die.’” 4 At this the serpent said to the woman: “You certainly will not die."
Satan then questions mans motive and integrity at Job 1:9-12
At that Satan answered Jehovah: “Is it for nothing that Job has feared God?10 Have you not put up a protective hedge around him and his house and everything he has? You have blessed the work of his hands, and his livestock has spread out in the land. 11 But, for a change, stretch out your hand and strike everything he has, and he will surely curse you to your very face.” 12 Then Jehovah said to Satan: “Look! Everything that he has is in your hand. Only do not lay your hand on the man himself!”
"You said in your heart, ‘I will ascend to the heavens.
Above the stars of God I will lift up my throne,
And I will sit down on the mountain of meeting,
In the remotest parts of the north.
14 I will go up above the tops of the clouds;
I will make myself resemble the Most High.’"
Just like that pilot, God is letting Satan take control of the world to prove his accusations.
1 John 5:19
"We know that we originate with God, but the whole world is lying in the power of the wicked one."
God recognizes that when Satan rules, Satan will go off course just like that jet. Satan teaches us false things about god. He distorts true worship. He imprints qualities of himself in man. 2 Timothy 3:2-5
"For men will be lovers of themselves, lovers of money, boastful, haughty, blasphemers, disobedient to parents, unthankful, disloyal,3 having no natural affection, not open to any agreement, slanderers, without self-control, fierce, without love of goodness,4 betrayers, headstrong, puffed up with pride, lovers of pleasures rather than lovers of God, 5 having an appearance of godliness but proving false to its power"
God comforts us through his son Jesus. Jesus teaches us about what is happening and what God promises for the future. 1 John 5:20
"But we know that the Son of God has come, and he has given us insight so that we may gain the knowledge of the one who is true."
1 John 3:8
"For this purpose the Son of God was made manifest, to break up the works of the Devil."
God is letting this all happen for a reason. There are other watchers, not just Satan. Satan rebelled and brought other angels out from God's house. By letting things play out this way, God will prove for all time that he the only one fit to rule. In a court case this would be considered a "precedent". In case this question should ever come up again, God has a precedent to show us he is the best ruler. Precedent definition
": a similar action or event that happened at an earlier time,
: something done or said that can be used as an example or rule to be followed in the future"
Satan's time is almost up. Satan has proved himself a liar and unfit to rule. God will be taking back control over the world. Jehovah God will then restore the world to its original purpose; That is: a paradise earth and on it perfect people who never die. This is basically what the bibles message is, shortened and paraphrased.