I think that a strictly linear view of history is problematic. The Faith was once for all delivered to the saints (Jude: 1.3), but the Faith is primarily Jesus Christ Incarnate, not a set of static, objective, definable beliefs. At the beginning, it is common for us to use various objective tools (logic, history, etc) to come towards Jesus Christ, but, at some point, we have to relegate all of those to a secondary role in our theology. We must submit everything to Jesus Christ, and specifically Jesus Christ crucified (1 Corinthians: 2.2). Logic, history, and everything else must be understood to have meaning only in Jesus Christ, and not primarily the other way around.
I've indeed understood your question as one of history but have not been able to find much more on the subject, either; I came across the same expensive book but have no experience with it. I'm trying to study some similar questions about early monasticism (which is itself a poor term encompassing numerous—and very different—lifestyles) and it is a little frustrating to see what appear to be large shifts at various points in history (not just the post-Reformation mess we deal with today, but very early shifts in thought and practice). However, thinking that those shifts necessarily have to do with whether a belief is right or wrong is not the correct perspective. Just as the Apostles—who saw Jesus Christ raised from the dead and still did not understand(!)—we cannot think that going back closer and closer to Christ temporally will get us any closer to understanding Him. The best way forward is not more history, but more prayer.