The rapture can not be post trib because if all the believers were raptured at the time of the second coming, there would be no one left in mortal bodies to live into the 1,000 year reign and re-populate the earth.
At the root of all is that the events of Revelation 20 are
not sequential to Revelation 19:11-21, for basically the same reason you point out here. There is no "rapture" ~ it can be neither pre-tribulation or post-tribulation. I think most here, if not all, understand Revelation 19:11-21 to depict the return of Christ... His second coming. If the events of Revelation 20 were chronologically sequential to Revelation 19:11-21, the inescapable implication would be that, since all Christ’s enemies have been/are destroyed in Revelation 19:11-21, then, regarding Revelation 20:1-6, there would be/is no one left for Satan to deceive in 20:3.
So the correct implication of this is, Revelation 20:1-6 is a "starting over," another, different vision of the same events preceding what is described in Revelation 19:11-21.
Revelation 20:1-15 is to be seen as a
seventh cycle leading to the Second Coming. It parallels all the other cycles,
rather than representing a unique period chronologically later than any of the others. This is the pattern, generally speaking, of Revelation itself as a whole; it is a series of different but parallel visions with regard to time. In other words, all these visions, which we might call cycles of judgment,
cover the same period leading up to the Second Coming. Moreover, later cycles concentrate more and more on the most intense phases of conflict and on the Second Coming itself, which we can easily see in the sixth cycle culminating in Revelation 19:11-21 and the seventh culminating in Revelation 20:7-15. The latter really ends at Revelation 21:8 and all evil is eliminated, whereas at the end of Revelation 19, only the "power source" of evil has been eliminated.
There is no "rapture," pre-tribulation or post-tribulation. We are in the time of tribulation now... now is the millennial reign of Christ, our King now, Who reigns now, and is with us in the person of the Holy Spirit now, just as He said He would be in Matthew 28:19-20:
"Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you. And behold, I am with you always, to the end of the age."
And one day ~ one great day, when this millennium is brought to a close, when, as Paul says, the fullness of the Gentiles has come in and the partial hardening that has come upon Israel is removed... in this way all Israel will be saved (Romans 11:25-26) ~ it will be brought to an end. All evil will finally be eliminated. The second resurrection will occur, alluded to by Jesus in John 5:28-29, and the final Judgment will ensue, as we see in Revelation 20:11-15 (alluded to by Jesus in Matthew 7:21-23 and depicted by Jesus in Matthew 25:31-46), and sin and death will finally be
completely defeated.
To God alone be the glory ~ Father, Son, and Holy Spirit ~ forever and ever!
Grace and peace to all.