Fall of Lucifer
Isa14:12-14 "How you are fallen from heaven, O Lucifer, son of the morning! How you are cut down to the ground, you who weakened the nations! For you have said in your heart: 'I will ascend into heaven, I will exalt my throne above the stars of God; I will also sit on the mount of the congregation on the farthest sides of the north; I will ascend above the heights of the clouds, I will be like the Most High.'
Lucifer, also known as Satan or the Devil rebelled against God for he wanted to be God and to sit on the throne of God, so that all will worship him as God.
Throne Given to Overcomers
Rev 3:21 To him who overcomes I will grant to sit with Me on My throne, as I also overcame and sat down with My Father on His throne.
So after the fall of Lucifer and before the foundation of the world, God chose weak and fragile men (not angels), created in His image, to be predestined to sit on His throne on condition that they can overcome the wiles of Satan.
Predestined 'Word made Flesh'
1Pet 1:19-20 but with the precious blood of Christ, as of a lamb without blemish and without spot. He indeed was foreordained before the foundation of the world, but was manifest in these last times for you.
God predestined that the Word was made in the form of a man and that through His sufferings as the Lamb of God, He will be able to help men overcome the wiles of Satan.
Heb 2:18 For in that He Himself has suffered, being tempted, He is able to aid those who are tempted.
Man Created in His Image
Gen 1:27; 2:16-17 So God created man in His own image; in the image of God He created him; male and female He created them.
God created men in His own image and gave them their free will. Men failed miserably when tempted by the Devil. Since then man worshiped idols and commit all types of abominations. Even the descendants of Abraham under Mosiac Covenant, with Yahweh displaying His presence, miracles, blessings, signs and wonders, yet they rebelled against Him.
The New Covenant
Rom 10:9 that if you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved.
With this new covenant, if anyone (not angels) chooses to believe the gospel (His death, redemption, resurrection, etc.) then he will be saved with the indwelling of the Holy Spirit.
Sons of God
Rom 8:16 The Spirit Himself bears witness with our spirit that we are children of God, and if children, then heirs -- heirs of God and joint heirs with Christ, if indeed we suffer with Him, that we may also be glorified together.
It was predestined that whoever suffers with Jesus, he will be counted worthy to be joint heir with Christ.
Gal 3:26 For you are all sons of God through faith in Christ Jesus.
Love for Jesus
John 14:23 Jesus answered and said to him, "If anyone loves Me, he will keep My word; and My Father will love him, and We will come to him and make Our home with him."
All Christians are called to love God. Almost every Christian will sing, praise, worship and declares that he loves Jesus, but many refuse to keep His word of forgiving his enemy, merciful, love one another, blameless, generous, kind, holy, humble, free from heresy, etc.
Even though these Christians choose to love Jesus, yet they did not keep His words, so God will not choose them for they do not love Him.
John 14:24 "He who does not love Me does not keep My words; and the word which you hear is not Mine but the Father's who sent Me."