My thought on why you see more communists, anarchists, and leftists in general in open source and federated platforms is that efforts centered around collaboration are likely to draw people who are more collaborative-minded.
Eventually logic and educated thought will drive them to somewhere else. Their ideas look great on paper but never live up to the hype. Human society doesn't cooperate well in groups larger than one hundred. You need strict rules and major punishments for large groups and that leads to an imbalance of power and authoritarian rule.