The answer from God’s word:
After the work of Jehovah, Jesus became flesh to do His work amongst man. His work was not carried out in isolation, but built upon the work of Jehovah. It was work for a new age after God had concluded the Age of Law. Similarly, after the work of Jesus ended, God still continued His work for the next age, because the entire management of God is always progressing forward. When the old age passes, it will be replaced by a new age, and once the old work has been completed, a new work will continue the management of God. This incarnation is God’s second incarnation following the completion of Jesus’ work. Of course, this incarnation does not occur independently, but is the third stage of work after the Age of Law and the Age of Grace. Each new stage of God’s work always brings a new beginning and a new age. So too are there corresponding changes in the disposition of God, in His way of working, in the location of His work, and in His name. No wonder, then, that it is difficult for man to accept the work of God in the new age. But regardless of how He is opposed by man, God is always doing His work, and is always leading the whole of mankind forward. When Jesus came into the world of man, He brought the Age of Grace and ended the Age of Law. During the last days, God once more became flesh, and when He became flesh this time, He ended the Age of Grace and brought the Age of Kingdom. All those who accept the second incarnation of God will be led into the Age of Kingdom, and be able to personally accept the guidance of God. Though Jesus did much work among man, He only completed the redemption of all mankind and became man’s sin offering, and did not rid man of all his corrupt disposition. Fully saving man from the influence of Satan not only required Jesus to take on the sins of man as the sin offering, but also required God to do greater work to completely rid man of his disposition, which has been corrupted by Satan. And so, after man was forgiven his sins, God has returned to flesh to lead man into the new age, and begun the work of chastisement and judgment, and this work has brought man into a higher realm. All those who submit under His dominion shall enjoy higher truth and receive greater blessings. They shall truly live in the light, and shall gain the truth, the way, and the life.
from Preface to The Word Appears in the Flesh
The work done at present has pushed forward the work of the Age of Grace; that is, the work in the entire six-thousand-year management plan has moved forward. Though the Age of Grace has ended, the work of God has progressed further. Why do I say time and again that this stage of work builds upon the Age of Grace and the Age of Law? This means that the work of this day is a continuation of the work done in the Age of Grace and an uplifting of that done in the Age of Law. The three stages are closely interconnected and linked one to the next. Why do I also say that this stage of work builds on that done by Jesus? If this stage did not build on the work done by Jesus, then in this stage the crucifixion, the work of redemption done previously, would still need to be carried out. This would be meaningless. Therefore, it is not that the work has completely finished, but that the age has moved forward, and the work has become even higher than before. It could be said that this stage of work is built on the foundation of the Age of Law and the rock of the work of Jesus. The work is built stage by stage, and this stage is not a new beginning. Only the combination of the three stages of work can be deemed the six-thousand-year management plan. This stage is done on the foundation of the work of the Age of Grace. If these two stages of work are unrelated, why is there no crucifixion in this stage? Why do I not bear the sins of man? I do not come through the conception by the Holy Spirit nor will I be crucified to bear the sins of man. Rather, I am here to directly chastise man. If I did not chastise man following the crucifixion, and now I do not come through the conception by the Holy Spirit, then I would not be qualified to chastise man. It is precisely because I am one with Jesus that I come directly to chastise and judge man. This stage of work builds entirely on the previous stage. This is why only such work can bring man to salvation stage by stage. Jesus and I come from the same Spirit. Though Our fleshes have no relationship, Our Spirits are one; though what We do and the work We bear are not the same, We are alike in essence; Our fleshes take different forms, and this is because of the change in era and the need of Our work; Our ministries are not alike, so the work We bring forth and the disposition We reveal to man are also different. That is why what man sees and receives this day is unlike that of the past; this is so because of the change in era. … Similarly, the Spirit of Jehovah is not the father of the Spirit of Jesus, much as the Spirit of Jesus is not the son of the Spirit of Jehovah. They are the same Spirit. Just like the incarnate God of this day and Jesus. Though They are not related by blood, They are one; this is because Their Spirits are one. He can do the work of mercy and lovingkindness, as well as that of righteous judgment and of chastisement of man, and that of bringing curses on man. In the end, He can do the work of destroying the world and punishing the wicked. Does He not do all this Himself? Is this not the almightiness of God? He could both set forth laws for man and issue commandments, and could also lead the early Israelites to live their lives on earth and guide them to build the temple and altars, reigning over all the Israelites. Because of His authority, He lived with them on earth for two thousand years. The Israelites dared not rebel; all revered Jehovah and observed the commandments. This work was all done because of His authority and His almightiness. In the Age of Grace, Jesus came to redeem the whole fallen mankind (not only the Israelites). He showed mercy and lovingkindness to man. The Jesus that man saw in the Age of Grace was filled with lovingkindness and was always loving, for He had come to deliver man from sin. He could forgive man their sins until His crucifixion truly delivered mankind from sin. During that time, God appeared before man in mercy and lovingkindness; that is, He became a sin offering for man and was crucified for the sins of man so that they may forever be forgiven. He was merciful, compassionate, enduring and loving. And all those who followed Jesus in the Age of Grace also sought to be enduring and loving in all things. They endured all suffering, and never fought back even if beaten, cursed or stoned. But that is not so in this final stage, much like how the work of Jesus and Jehovah was not alike though Their Spirits were one. The work of Jehovah was not to bring the age to an end but to lead it and usher in mankind’s life on earth. However, the work now is to conquer those deeply corrupted men in the Gentile nations and to lead not only the family of China but the entire universe. … The Spirit of God has done such great work since the world was created; He has done different work across the different ages, and in different nations. The people of each age see His different disposition, which is naturally revealed through the different work that He does. He is God, filled with mercy and lovingkindness; He is the sin offering for man and man’s Shepherd, yet He is also judgment, chastisement, and curse on man. He could lead man to live on earth for two thousand years and also redeem the corrupt mankind from sin. And this day, He is also able to conquer mankind who does not know Him and make them subject under His dominion, so that all submit to Him fully. In the end, He will burn away all that is unclean and unrighteous within men in the entire universe, to show them that not only is He a God of mercy, lovingkindness, wisdom, wonder and holiness, but even more, He is a God who judges man. To the evil among all mankind, He is burning, judgment and punishment; to those who are to be perfected, He is tribulation, refinement, and trial, as well as comfort, sustenance, supply of words, dealing, and pruning. And to those who are eliminated, He is punishment, as well as retribution. Tell Me, is God not almighty? He can do all work, not just the crucifixion as you imagined. You think too lowly of God!
from “The Two Incarnations Complete the Significance of the Incarnation” in The Word Appears in the Flesh