The overwhelming majority of the early church leaders (fathers) were premillennial and believed in a literal 1000 yr. kingdom. Today, 2/3 of Christians are amillennial. I do not want to imply that amilennialists, are not Christian.
Nevertheless, that view is one that rejects the notion that Jesus Christ will physically reign on the Earth for exactly one thousand years. Rather, they interpret the "thousand years" mentioned in Revelation 20 as a symbolic number and not a literal duration of time. Amillennialists hold that the millennium has already begun and is simultaneous with the current church age.
This is what lead to the success at the doors I experienced when I was a regular pioneer for Watchtower. I regularly held 8-10 bible studies per month. Most of us were just ignorant pawns and didn't realize the theological landscape we were in.
The Kingdom message was attractive to many people because they never heard about a literal kingdom at their church. When a lady pointed out to me that hundreds of millions of people already believed in a literal "God's Kingdom", I was shocked and stopped going in field service.
The Watchtower used this "conversation opener" to spread the false message that there was another salvation method other than Christ as our personal Mediator / Savior - for the "great crowd". The unique WT views on the 1.) tripartite nature of man, 2.) 1914 invisible return of Christ along with 3.) the rejection of the Rapture, further supported their end times deception that Christ as a "personal savior" was not needed and not available.
For those wanting to understand the premillennial view of the end times (which is virtually synonymous with the early congregation leaders in the first 3 centuries after Christ) , the following talk is very helpful. It identifies who the great crowd is according to historical and accurate views handed down from the apostles. It will also walk you through the general framework of literal biblical end-times theology.
https://www.youtube.com/watch?v=Tw3VLpd9Fm0&ab_channel=GracetoYou