God has a purpose for whatever He does. Whatever He feel appropriate is what He does. That is the more reason why there is sacrifice in various means. God could harden the heart for a purpose which could eventually be seen as beneficial for humanity. When God sacrificed part of Himself to enable all humanity to get life and existence, it had a general benefit for all humanity.
He took away part of Himself to form billions of souls which would which would be given body and flesh to live as humans. That is the reason why God is said to have created humanity in His own image. The soul is part of God’s own image which was taken out of Him. For that reason God is said to be within everyone. Due to that, the body has become the temple of God. It is called temple simply because where God resides is a holy place and therefore called a temple. That is the reason why Paul stated that if anyone spoils the temple of God, such a one would also be spoiled.
The purpose for the creation of man was that, after acquiring body, each soul would come to earth to be trained how to live peacefully with others. After one has successfully gone through the training ad qualified for eternity, the soul returns well equipped with the experience of living peacefully with other souls for ever and ever. To achieve that purpose, there was the need to sacrifice Lucifer and some of the angels to come down to earth for the assignment of training all humanity.
The presence of God is always full of joy and happiness ( ). So if Lucifer and the team of angels had been asked to leave His presence for such an assignment, they would be sad. Even though they could not have objected, they would always feel they had been deprived of their joy. And God would not be pleased to see His messengers sad and working grudgingly. Therefore there was the need to harden their hearts to rebel in order for them to be sacked. But after being sacked, God came down to meet them on earth and assured them that they were pardoned, but they were to complete such and such assignments and at the end of it, they would come back to resume their positions in Heaven. Then Lucifer and his team became so happy. When the angels in heaven were later briefed by God, they all jubilated ( ). the actual hidden truth was not revealed to John in his Revelation because it was not yet the predestined time. Now is the predestined time for humanity to feel the full responsibility for their sins as there is no enemy who had influenced them to sin. The hidden reason of the jubilation of the angels left in heaven were that their colleagues were forgiven. Even though it was stated that they jubilated because Lucifer, now branded as Satan had been defeated. God could have said the same words that He used to call them into existence for them to be annihilated or vanished from existence. Furthermore, the angels left behind were not part of the team that had left the joyful presence of God to be on earth serving the needs of humanity till the end of the earth.