This is what the title asked, but no one seems to have addressed it.
There are multiple reasons for the Second Coming of Christ "with power and great glory", but the main purpose is for the Lord Jesus Christ to literally (and eventually) establish God's Kingdom on earth, and destroy all other kingdoms.
So here is the sequence of events and everyone should search out the relevant Scriptures regarding all this (Revelation 19-21):
....
There's actually more detail revealed in God's Word about all that.
1. Jesus returns on the "day of the Lord", the LAST day of this present world.
2. On His descent to the Mount of Olives east of Jerusalem on earth, the dead saints are resurrected first, and then the still alive saints on earth are gathered with them, to Him, and all head to the Mount of Olives on earth where His feet touch down, and there is a great valley formed there by that event.
3. Per Jesus in John 5:28-29, ALL... the dead, both the asleep saints, and the wicked dead, are resurrected on that day of Jesus' 2nd coming. The idea that the wicked dead are not raised until after the 1,000 years is over is a myth, a tradition of men that comes from their not understanding what the Rev.20:5 "
dead" that lived not again until... the 1,000 years are over ' actually means.
The Revelation 20:5 "
dead" represent
SPIRITUALLY dead souls without Christ.
Jesus showed us about this '
spiritually' dead idea in The Gospel. He mentioned how the blind scribes and Pharisees were like beautiful whited tombs on the outside, but inside were full of dead men's bones (Matt.23:27). He was pointing to their soul being
spiritually dead inside their flesh, like dead men's bones inside the tomb, but their tomb as their outside flesh with trying to appear clean and holy. He also compared them to graves that men walk over and are not aware. This is what the idea of the "
dead" of Rev.20:5 actually means, and what Jesus showed in The Gospel about the blind scribes and Pharisees in comparison is not the only reason...
Recall Jesus per John 3 where He told Nicodemus that to enter the Kingdom of God one must be
"born again", of water and of The Spirit. Jesus said that which is born of the flesh is flesh, and that which is born of Spirit is spirit. Jesus revealed there are TWO DIFFERENT DIMENSIONS OF EXISTENCE by that, this earthly one of material matter, and the heavenly one of Spirit. We have inside our flesh body another... body, but of Spirit, of that other dimension not of flesh. Apostle Paul clearly revealed this in 2 Corinthians 5 about our other body, our spirit body from God that is eternal in the heavens.
On the day of Jesus' future return, ALL... those still alive on earth will be 'changed' at the twinkling of an eye to their spirit body, the flesh being cast off. At the same time, ALL the dead will be raised to that same spirit body, the resurrected body of 1 Cor.15 which Paul called a
"spiritual body". Brethren that don't understand this as written, are still living in the dark ages about the make up that God made us with. The future
"resurrection of life" is NOT to another flesh body. Per 1 Corinthians 15:50, Paul said flesh and blood cannot enter into the Kingdom of God, neither does corruption inherit incorruption.
Thus the John 5:28-29 Scripture by Lord Jesus shows the Revelation 20:5 "
dead" actually means the
"resurrection of damnation" that are raised on the day of Christ's 2nd coming at the start... of the 1,000 years of Rev.20. Their souls will still be in a spiritually dead, liable to die condition subject to the "second death" of the "lake of fire". They will be in that type of condition throughout the whole 1,000 years reign by Christ and His elect.
Apostle Paul actually covered this concept about the spiritually dead which will include the wicked still alive on the day of Christ's 2nd coming. The still alive wicked will also... be 'changed' on that day of Christ's coming. The pop myth pushed by many in today's Church that only those in Christ will be 'changed' to the "spiritual body" per 1 Cor.15 is a just that, a pop tradition, a myth from not fully understanding Paul.
In 1 Corinthians 15:53-54, Paul used FOUR SEPARATE Greek words to define a change from our flesh body, to the spiritual body, and the condition of our dead soul being changed to an immortal soul by Faith on Christ. Most don't take the time to look up these 4 different words in the Greek...
1 Cor 15:53
53 For this corruptible must put on incorruption, and this mortal must put on immortality.
KJV
1. "corruptible" = flesh body
2. "incorruption" = "spiritual body", the resurrection body
AND
3. "this mortal" = a mortal still liable to die soul
4. "immortality" = the soul made immortal by Faith on Jesus Christ
Those blind scribes and Pharisees which Jesus rebuked, that 1st change ONLY will apply to them, their mortal souls will STILL be "dead" in that future time of Christ's 1,000 years reign.