Journeyman, been reading through this thread again, and you question got my attention. Let me share some insights that perhaps will satisfy your question, "why does salvation come now." Following is a commentary on
Rev.12:7-12. (Bear in mind, each event within prophecy gets time stamped when it is fulfilled.)
Rev. 12:7
And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels,
{7} There was a war in Heaven. Michael (the name which Jesus used before coming to Earth as a human)39 and His angels fought against the great red dragon and his angels.
A few hours before His death, Jesus made the following statement: “ ‘Father, glorify your name!’ Then a voice came from Heaven, ‘I have glorified it, and will glorify it again.’ The crowd that was there and heard it said it had thundered; others said an angel had spoken to him. Jesus said, ‘This voice was for your benefit, not mine. Now is the time for judgment on this world; now the prince of this world will be driven out.’ ”40 Jesus knew that Lucifer would be permanently cast out of Heaven if the Father approved His sacrifice. When Jesus said, “Now is the time for judgment on this world. . . ,” He meant that the time had come for the Father to determine who should be the rightful prince of this world. When Jesus said, “now the prince of this world will be driven out,” Jesus predicted the war described in verse 7.
This war occurred on Resurrection Sunday.
Rev. 12:8, And prevailed not; neither was their place found any more in heaven.
God did not destroy the devil and his angels on Resurrection Sunday because His purpose for them was not finished. God permitted open warfare in Heaven between Lucifer and his angels and Jesus and his angels for a significant reason. The Father wanted to make sure that among the holy angels, no sympathy for the once adored and highly exalted Lucifer remained. This war was not a test of faith as the first war had been.41 This war produced a revelation. The Father allowed the battle to last long enough to see where each angel firmly stood. After 4,000 years, there was no change. Those loyal to Lucifer defended their evil leader and remained unchanged. Those loyal to Michael also remained unchanged.
Rev. 12:9
And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
{9} Once the loyalty of the angels was confirmed, the devil and his angels were once again thrown out of Heaven, at the speed of lightning.42 The Father threw the devil and his angels into an earthly abyss and confined them there.
And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
Ever since Resurrection Sunday, the devil and his angels have been bound to this planet, limited to the dimensions of the spirit realm (represented to John as the abyss). Originally, the great red dragon and his angels were hurled out of Heaven because of defiance. Four thousand years later, their defiance remains unchanged. The great red dragon is that ancient serpent called the devil, or Satan, who leads the whole world astray. He was hurled into the Earth, and his angels with him.
Rev. 12:10
And I heard a loud voice saying in heaven, "Now is come salvation", and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night.
{10} After the war in Heaven ended, I heard a loud voice in Heaven say: “Now that salvation has been paid in full and the devil has been defeated, the gospel of Jesus Christ and His coming kingdom will advance with clarity and power throughout the Earth. Lucifer’s position as “the prince of Earth” has been honorably overthrown by the perfect life, ministry, death, and resurrection of Jesus Christ. The accuser of our human brothers, who accuses them before God day and night, has been hurled down and his endless arguments and accusations in Heaven against repentant sinners have been silenced.”45
Rev. 12:11
And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death.
{11} The voice continued: “Even though our brothers on Earth are sinners, they are not hopeless or defeated. Lucifer’s claim that God cannot legally justify sinners has been silenced because Jesus paid the price for every sinner who surrenders to the directives of the Holy Spirit and the gospel of Jesus Christ. Through faith in Christ, repentant sinners are covered with Christ’s righteousness (justified as though they never sinned) in God’s sight.”46
When a person surrenders to the directives of the Holy Spirit, he honors and upholds the Word of God at all costs, and the word of his testimony proves that he is loyal to God, even willing to die for Him if necessary.
Rev. 12:12
Therefore rejoice, ye heavens, and ye that dwell in them. Woe to the inhabiters of the earth and of the sea! for the devil is come down unto you, having great wrath, because he knoweth that he hath but a short time.
{12} “Therefore, rejoice holy angels, all of you who live in Heaven because atonement for sinners has been paid in full, but woe to God’s people on Earth for the devil’s wrath is upon you! He is filled with fury, because he now knows that he will fail miserably.
* Note - At the fifth trumpet, the devil and his angels will be permitted to exit the abyss. Therefore, a time is coming when the devil and his angels will physically appear before the people of Earth.43 At the Second Coming, Jesus will destroy the bodies used by the devil and his angels and Jesus will return them to the abyss (spirit realm).44
Taken from: Jesus’ Final Victory, pg. 301
So, a more direct answer to your question is this. Until Christ came and lived a life that fulfilled the requirements of the ten commandments, (written by His own finger,) then was willing to die, the second death, (which the law required if broken,) salvation would not be possible for fallen man. All of the animal sacrifices mandatory before the cross, pointed to the death of Christ, and was based on faith that Christ would fulfill the Fathers requirement that He,Christ, would be The Lamb of God/the Father. On resurrection Sunday, the words,
"Now is come salvation" (Rev.12:10,) was fulfilled.
Had the Father not excepted the life of Christ as fulfilling the requirements of the ten commandments, Christ blood would not have atoned for fallen man, and the Father would not have raised up Christ, and fallen man would have been without a savor, thus the Fathers plan of salvation would have failed, and man would have had to atone for their own sins and die the second death.
Hope this makes sense and answers your question.