A few years ago, Reddit strategically banned two terrible subreddits during one of their shitstorms (the whole AMA firing scandal), just as Voat was getting popular. It turned from a decent community that was starting to grow and challenge Reddit’s presence, to a right-wing extremist cesspool overnight.
You also see this sort of thing happen to subreddits all the time. Some of them go from a good community, and either slowly or quickly, shifts into a much more terrible version of itself. Russian bots/ops have transformed subs to push their own agenda.
The community matters, and how that community evolves matters a great deal. Communities can live or die from massive migrations like this.