For some strange reasons a small segment of free marketers insist they are anarchists, but they are an extreme minority fairly disconnected from the anarchist movement. Even the primitivists tend toward communalism. Anarchists will work with non-anarchist communists. There are leaders in the anarchist movement, make no mistake about that. What is different about anarchists is that we distrust leaders in general, and demand instant accountability.
Leaders are fallable.
Theoriticians make mistakes. People are blinded by their own privilege. Anarchists recognize that and seek to check the power of individuals over others at every turn. If a leader has good ideas that people agree with, then people will act on those ideas. But simply because someone had good ideas in the past does not mean that their ideas will be good in the future.