There's a bunch of people who think Jesus's Millenial Kingdom happened on earth already and that our minders have played with historical timelines to hide it.
Usually they're people studying a theorized "mud flood", or "Tartaria" or even maybe "The Carrington Event".
Have you heard of these?
I watch a YouTuber named Jon Levi, who's videos are pretty interesting, but I don't quite know what to make of it. His -as well as others'- arguments are compelling.
I just don't know.
Revelation can be hard to figure out, but in the end, I don't WORRY about any of it. We'll know what we need to know, when we know it.
Maybe not everything spelled out in Revelation happens in chronological order.

I watch Levi's videos every week. The dude literally cracks me up with his sarcastic sense of humor. Hes definitely on to something no doubt about it.

According to my understanding if we already had the millennial 1000 year reign we would already be in the eternal state with the New Jerusalem etc and Satan would already be in the lake of fire.

Hoping for more disclosure of a lot of hidden stuff that might help us.

Revelation 20: 7-8
After the millennial kingdom,
“ . . . Satan shall be loosed out of his prison”

[since our timelines and history are so corrupted, we could be living through a post-millennial-kingdom era, imo]

5 But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection.

6 Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years.

7 And when the thousand years are expired, Satan shall be loosed out of his prison,

8 And shall go out to deceive the nations which are in the four quarters of the earth, Gog, and Magog, to gather them together to battle: the number of whom is as the sand of the sea.