Then explain why the kingdoms of earth are become His kingdoms at the 7th Trumpet.
Revelation 11:15
No one is denying the reign of Christ now. Amil deny the coming Day of the Lord, that is prophecied to start at the conclusion of the 7th Trumpet. The will of the Lord will be in earth as it is in heaven, at the 7th Trumpet.
Building a kingdom is one thing. Enjoying that kingdom is the Day of the Lord.
The Day of the Lord that is coming when the seventh trumpet begins to sound is the last day of this Church and Gospel age. The seventh trumpet does not usher in more time on this earth that premillennialists imagine will last ONE thousand years. The sounding of the seventh trumpet is when time or opportunity to be saved on this earth shall be finished.
Revelation 10:5-7 (KJV) And the angel which I saw stand upon the sea and upon the earth lifted up his hand to heaven, And sware by him that liveth for ever and ever, who created heaven, and the things that therein are, and the earth, and the things that therein are, and the sea, and the things which are therein, that there should be time no longer: But in the days of the voice of the seventh angel, when he shall begin to sound, the mystery of God should be finished, as he hath declared to his servants the prophets.