I'll answer this question by focusing on the Zapatistas. The reasons will be slightly different but broadly similar with regards to other groups.
Many anarchists face a tension between wanting to see an increase in resistance and rebellion, and wanting that resistance to occur in an antiauthoritarian way. Every anarchist strikes a particular balance between these two desires.
When a struggle blooms in another country, it is hard to evaluate to what extent the struggle is libertarian, what is the likelihood it will create a new oppressive authority, and so forth. It is even harder nowadays that most authoritarian revolutionary groups have adopted a libertarian rhetoric since the discrediting of Marxism and the generalization of certain parts of a libertarian ethos.
Also, anarchists along with most other people tend to disagree on questions of cultural relativism: to what extent does a different cultural context justify behavior or politics that we would find unacceptable or disagreeable in our immediate surroundings? To what extent do we have a right to criticize practices that are born of a different historical and cultural legacy?
In the case of the Zapatistas, Marcos is an extremely effective propagandist and charismatic figure, which immediately elicits the profound distrust of some and the profound admiration of others. On top of this, in the years after 1994 most of the information to arrive in other countries from the Zapatista communities stressed how different this movement was from the Marxist-Leninist and Maoist guerrillas of the previous decades in Latin America. And in fact, Marcos has positioned himself far to the left of Chavez and Morales, something even many North American anarchists have refused to do, preferring like Michael Albert to build solidarity with tenured and salaried leftist politicians in South America rather than with proletarian and indigenous anarchist comrades who have been highly critical of these figures.
For example, I know criticisms exist of Zapatista authoritarianism and cronyism, but I would not know where to find published accounts of such criticism. Books in favor of the Zapatistas, on the other hand, abound.
So the question is not only one of different standards among anarchists regarding cultural relativism and necessary minimums of antiauthoritarians, but also of access to information. We all know the Zapatistas are not anarchist, and for most of us that's okay. What remains unclear is to what extent the Zapatista project is a state-building project.