You know several times people have posted this, but without much evidence.
People leave, sometimes due to Life, or they die or they get tired of posting or they find a better outlet - or indeed they don’t like the way other posters behaved. I only know of one that gave that last reason. Most of the rest- just left. Also Conservatives posters left, and posters of all types, shapes and forms. You may have an option that people left as the board moderation did not squelch argumentative, bullying, harassing, and trolling posters, but there is damn little evidence that really happened. Others likely left as board moderation did squelch argumentative, bullying, harassing, and trolling.
And do note- being argumentative is part of why this board is here, and bullying and harassing are still okay in the PIT, iirc (but admittedly not for homophobic or racist reasons). For some reason, the idea that a poster might leave if they were bullied in GD- but laugh it off and think it is just peachy-keen if said bullying is in the Pit is prevalent here. And wrong.