I don't believe that's entirely true - the people who took part in the councils and debates were frequently Bishops or similar leaders of a Christian congregation or community, and since a proper clerical hierarchy had yet to be established, these leaders would often be raised up by the community there were a part of. Sure, they were bigwigs, but I'd say they would often be local bigwigs, speaking for the community they were leading or representing to outsiders.
So in a very real way, these newly minted Christian theologicans represented distinct Christian communities with their own collective views and practices, and the question of heresy was very often a conflict between these different communities and their particular practices or interpretations. (e.g. the Monophysite conflict was very clearly a conflict with the Christian communities of Alexandria)
Cool! Yeah, that is true, but really my picture was such a broad one that it was meant to represent a variety of centuries and even the general expectations one would have for how religions tend to operate, where the majority of ordinary folk have usually been illiterate and dealing with very loose magical folk concepts more than they are deeply familiar with theology. In some of the earliest stages, Paul seems to have been slightly disturbed or annoyed by how easily major issues and differences could occur in communities that were just at a little distance than others, due to a lack of constant monitoring or control, where a diversity of ideas and behaviors which were not expected or sanctioned would creep in or were feared to have creeped in. There seems to be evidence at least that the regular population throughout the centuries were a much larger quantity of people than the particular theologians attending councils, and that the dispersal of news from such councils may not have always been easy to make everyone aware of.
Christianity spread all over the place eventually, and again, the popular Christianity practiced by and known to the ordinary folk was highly unlikely to be very literate, and was much more likely to be more about tradition, ritual, magical types of practices, superstitions, praying to saints eventually and looking to relics, not a deep familiarity with the contents of the Bible which may have remained inaccessible in their local languages or dialects, as literacy was also not prevalent and the poorer classes were always the larger in amount in a pyramid like structure. To become a theologian was in some cases a way to raise status and escape certain class issues, but it was difficult for much benefit to be returned to the communities which sent their best and brightest or most ambitious or capable for theological learning or apprenticeship. Furthermore, the same sexual evils that we hear about today, were likely widespread in the past, and the structures of abuse and predatory cliques were all the more likely, as has been demonstrated even among the Buddhist monasteries lately (but were more than likely always the case, because of how they are designed perfectly for evil people to take advantage of).
So, of course I have no idea how things were in the remote past, I don't even know what the people in the apartment unit next to me are actually doing (but it sounds like very loud and obnoxious sex), I suspect the story which most accurately represents the broadest scope of time and Christian history is one where:
The majority of the people are poor, of a lower class than the smaller population of academics and elites and nobles.
The majority of the people are prone to magical thinking, are more familiar with traditions and superstitions than with theological nuances.
The majority of the people know very little of the Bible or theological discourses or council decisions or whatever, but are mainly ignorant people.
They worship a cosmic and magical folk Jesus who has miraculous powers simply called upon by name like a Bodhisattva, but is God or connected to God in some fashion. They also know of various Biblical stories and characters, but only vaguely, and unlikely to know straight scriptures.
The clerics keep reciting things ritualistically and like mantras to the illiterate masses with a poor grasp on linguistics or meaning even, and this continues even when the languages become increasingly archaic or foreign as Christianity spreads.
People would send some of their children to positions or educations if they could, to raise their status, it is more than likely these children entered into networks of systematic abuses and controls which only allowed certain secret keeping members to continue and succeed, and these networks of abuse and control were sometimes embedded almost as traditions for very long spans of times with generations of abusers and their abusing heirs, which may have forced many of the children sent into these systems to not have much real influence to save the majority of their communities or remain loyal to such, but some families were able to excel more with the help of such, but needed other members to do certain things to, I'm thinking of families which had this as part of their plan, usually led by a strategic sort of elder male of the family who uses his children like pawns.
The best Christians throughout history have likely been certain theologians and certain innocent or mainly ignorant devout people, following traditions of shame and decency and morality. I think it is very possible that the vast majority of people were generally humane and decent, with a lot of corrupt and villainous folks from all levels of society interspersed, probably at a rate and level similar to the rates of the criminal and corrupt elements or unethical or cruel people in today's society (most of which remain unknown to us, but are causing problems among their networks of contacts).
Magical vague Christianity remains the mainstream norm to this day, but now it seems even lighter on the ritual or practices than ever before, even with a much higher literacy rate and availability of scripture than had ever been possible.
Christians mainly don't syncretize, but if they do, it could be said (not very seriously), that many people who identify in some way as Christian, also generally accept the norms of the governments they live under, society, modernism, science, etc, with only minorities resistant to such, and so Christianity has mainly syncretized with the mainstream culture and mainstream mythology, where we all basically know of the same characters and sayings. Furthermore, other people identifying as other religions are also mostly part of the modern norms and culture, which is largely regulated or has the ideas dispersed through the media, the internet, and vast cross cultural contact, imitation, production, and distribution, as well as easy access and availability. We are, contrary to what people may think, closer to a One World Culture than has ever been the case in the past, and it could be considered in some ways a synthesis of many things, a syncretism, where everyone basically accepts the same ideas, thinks that God means generally the same God whether they accept it or deny it, talk about the same Jesus even if they are from other religions, and know about Spiderman and Superman, even Hitler as a villain and whatever as well as ideas very widespread across the whole globe now.