What exactly do you think causes echo chambers? When algorithms inSocial networks reward bad behaviors bad behaviors will dominant. One of those bad behaviors is lazily espousing the dominant viewpoints in pursuit of social acceptance. Another is avoiding broadcasting certain beliefs out of fear of holding the unpopular opinion. Who disagrees with a highly comment? These are the behaviors which create mono cultures and echo chambers.
I don't think echo chambers are necessarily as maliciously or narcissistically inspired as you do. They are a natural result when people have complete control over what they hear and they primarily seek to hear things that reinforce their existing worldview.
But we didn't have natural echo chambers of that sort and magnitude, because we didn't live in a global village.
I believe that the ideological self-segregation is mostly because you can choose who to interact with. That's also why it's primarily online, because you cannot choose to a similar degree offline, and the physical distance between you and your near-duplicates is too large for echo chambers to form, unless you make an intentional move to bring them together (e.g. sects moving to a certain location).
