I think your "effectively controlled" is mostly meaningless. There's orders of magnitude of difference between "started off as scattered and big companies now

I think your "effectively controlled" is mostly meaningless. There's orders of magnitude of difference between "started off as scattered and big companies now do a majority of the maintenance" vs actually CENTRALIZED, like Twitter. My website and my email, from my domain, both exist generally as equals without any meaningfully strong influence from google or whatnot, e.g. censoring my website would be a practically completely different thing from the ridiculous mess that Twitter is becoming (if it isn't already.)