One example might help reinforce my case. Note to commenters, I am not making any judgements on these communities, these are just my observations.
A hard left community which is heavily invested in identity politics is inherently vulnerable to this type of destruction. It is in the DNA of the movement. I have witnessed this in many groups.
Group starts building large number of members for a cause, lets call it "Womans March". Initially all unified behind a common cause. Exploit identity politics to break it.
"Wow, I can't believe ALL the admins are white woman" "smh, these people need to stay in their lane and lets POC take charge" "my trans* friend was just messaged by an admin telling them "men" aren't allowed" "some of the people on this page are too ghetto"
As long as the culture is focused on grievance and division, they will divide and divide with a miniscule amount of pushing. Resentment and infighting grow almost exponentially.
A group of 5 co-ordinated trolls using these tactics collapse massive communities over and over again. You would not believe how effective it is. These are all old CIA tactics, unclassified manuals are studied and disseminated.