Getting right to the point: in this commentary, my first book, The Seventh Trumpet has Sounded, I emphasize that the kingdom of God (Christ) has already been established. Christians are now in the kingdom; it's not something yet to occur in the future. I contend the "seventh trumpet" in Revelation has "sounded." It "sounded" in the first century resulting in the kingdom being established and that several other events occurred as a result.
I emphasize from the beginning of this commentary and repeat several times Paul's instruction in 2 Timothy 2:15, "Be diligent to present yourself approved to God as a workman who does not need to be ashamed, accurately handling the word of truth." I have almost a "mantra" when teaching and emphasize in this book to "pay attention to every word." "Pay attention to what the text of the Bible says." Do not ignore facts established throughout the Bible if any conclusion we have on any subject contradicts facts already established, and do not speculate. We may give an opinion, but opinions are not necessarily consistent with truth.
For any person to believe that the establishment kingdom of Christ is something yet to happen sometime in the future, and believe that is a message in the book of Revelation, that person has to be unaware of, or ignore, what Jesus and His apostles said about the kingdom when He was here on the earth.