Eternity was interrupted by war
The actual conflict in eternity was only the beginning of the war in heaven. It was more like a disagreement than a shooting war. The two Archangels disagreed on how God’s created beings, the spirits, should be led throughout eternity.
The disagreement is not about having or not having a material world. This part of their disagreement only occurs after the war in eternity erupted and Lucifer lost.
Michael and Lucifer are the only two Cherubim or Archangels. They are like God’s Generals in charge of God’s creation. Michael and Lucifer are created beings, spirits, like the rest of us. Only their rank differed from us.
The dispute was over the operation of God’s creation. Lucifer, later renamed satan and the devil, believed they should be lords, like dictators or kings, over the creation of God; while Michael believed God wanted them to be administrators to assist the creation of God. The difference is simple. Lucifer wanted people to serve him, and Michael wanted to serve people.
The conflict erupts due to the interpretation of God’s Will, or God’s instructions given to them at the time of their creation. These instructions were not written instructions, neither were there any higher authorities or courts to submit the matter to be interpreted.
The Archangels, like us, only had their instincts superimposed inside their own brains at the time of creation, and it was now up to them and their own free will to determine what God wanted them to do with their instinctual information.
No physical engagements occurred between them in the eternal world, prior to the creation of the earth and the universe, as in a shooting war. The Archangel that made the correct decision based solely upon the instincts God implanted in them would result in God empowering that Archangel, thus making one Archangel more powerful than the other. Michael made the correct decision and God empowered him. So he could overpower Lucifer.
The conflict interrupts eternity for a moment called Time
The creation of earth and the universe was always on God’s drawing board, scheduled to be an eternal paradise for His created beings.
An automatic rule kicked in when the conflict erupted in eternity between the two leaders of God’s spirits. It interrupted the plan for planet earth. The interruption would cause the earth to become a temporary prison for Lucifer (satan) and his followers, who were still spirits.
The birth of all spirits as human beings on earth was God’s plan prior to the conflict. The beginning of God’s creation would have been people born into a paradise; but now an automatic switch had been thrown by Lucifer’s act and misinterpretation of God’s original instructions.
Once Lucifer made his decision to resist God, things took on a life of their own. God did not sit and judge the situation, since God already knew exactly what Lucifer would do.
The only changes in God’s eternal plan would be the order of people born on earth, and the separation of spirits after life on earth ceased to exist for each person, which is physical death. Needless to say, it was part of God’s plan, and built into the system.