"Communities" don't actually exist beyond the beliefs of their current membership. Its like a philosophical discussion of mind-body dualism. Arguably, for example, Twitter quite literally has no soul, its belief system is merely the sum of its current participants. The concept of twitter having a soul is perfectly analogous to the concept of a human being having a soul in the biblical sense.
A small group can have values divergent from the mainstream. By definition if a group scales up to mainstream, the group's values at mainstream scale will be mainstream because its members ARE the mainstream, or optionally some kind of cabal will have to spend infinitely increasing effort on mass censorship and intense propaganda (see contemporary issues in legacy social media).
Now if your entire economic system depends on growth for the sake of growth, all small groups will eventually tend toward mainstream beliefs or they will shut down.
Not all orgs are "successful" like the "forum for doctors" example. The OP considers "Dr Phil" and "Dr Oz" but WRT influence almost no doctors out there are Dr Phil or Dr Oz and most people are not fans of their TV shows. Consider dying legacy media like newspapers and TV and "Hollywood" in general. Fewer people pay attention to their antics every year. Eventually those orgs WILL collapse and disappear, like newspapers have been slowly doing, but for now, a lot of money can be made off really bad, non-influential movies, for example. Shrinking organizations can aggressively gatekeep their belief systems until the org shuts down completely. For example, you can make a lot of money off publishing a book almost no one reads, but don't confuse that pile of money with influence.
Ironically the people gatekeeping an organization via censorship, propaganda, etc, truly THINK they are saving the org by being devout believers in the Current Thing, but they're actually destroying the org. If you have no traction, the harder you push the further you get away from the mainstream, no matter how much those whom are pushing would like to think they're moving the mainstream.
A small group can have values divergent from the mainstream. By definition if a group scales up to mainstream, the group's values at mainstream scale will be mainstream because its members ARE the mainstream, or optionally some kind of cabal will have to spend infinitely increasing effort on mass censorship and intense propaganda (see contemporary issues in legacy social media).
Now if your entire economic system depends on growth for the sake of growth, all small groups will eventually tend toward mainstream beliefs or they will shut down.
Not all orgs are "successful" like the "forum for doctors" example. The OP considers "Dr Phil" and "Dr Oz" but WRT influence almost no doctors out there are Dr Phil or Dr Oz and most people are not fans of their TV shows. Consider dying legacy media like newspapers and TV and "Hollywood" in general. Fewer people pay attention to their antics every year. Eventually those orgs WILL collapse and disappear, like newspapers have been slowly doing, but for now, a lot of money can be made off really bad, non-influential movies, for example. Shrinking organizations can aggressively gatekeep their belief systems until the org shuts down completely. For example, you can make a lot of money off publishing a book almost no one reads, but don't confuse that pile of money with influence.
Ironically the people gatekeeping an organization via censorship, propaganda, etc, truly THINK they are saving the org by being devout believers in the Current Thing, but they're actually destroying the org. If you have no traction, the harder you push the further you get away from the mainstream, no matter how much those whom are pushing would like to think they're moving the mainstream.