If you try to pin the blame on any particular person in this event I think you are missing the point. CRM is Crew Resource Management. And one of the most valuable lessons learned from this accident was in fact that you have to think of the crew in a completely new way. The performance of the crew is not determined by the most skilled member, but it is determined by how well it functions as an entity.
Van Zanten may very well have been sure about what he assumed at the time. But the point here is that you shouldn't pinpoint his assumption as the reason for this accident. Today we may call it bad CRM that none of the other crew members intervened, but you also have to put the whole thing into its correct context, that is, into the 70s, when nobody talked about CRM. It wasn't a way of thinking back then. Thus you can't argue that the reason for the accident was bad CRM, since it was not something that had even been discussed as a subject back then.
What did come out of the accident, however, was a completely new way of thinking. And that way of thinking came to be known as CRM.
If something like that happened today we could very well point out disfunctional CRM as a reason for an accident, because we all know how it should work in theory. At the time of the accident however, Van Zanten and all the other crew members had a way of thinking which was in accordance with the culture of that time. They can't be blamed for that, they were just victims of it. I don't think anybody would really believe that Van Zanten ruled the cockpit with an iron fist. His way of doing things probably wasn't better or worse than the ways of anyone else at that time.