Just a wild stab at "fuzzy" logic from non-professional:
They were going down and they could not understand what is going on for an extended period of time. That can mean that by that time they also ceased to trust some of their instruments. So what did they believe from the data they were seeing or assuming? That can be deduced from the only constant in their behavior: "stick held fully back" most of the time. In any dangerous situation with unreliable information present, you are relying only on those information that you assume to be most reliable, and you are doing only what is most important for the moment. You will stop falling that way only if you have forward speed, so that must be what they thought to be most reliable of the important information. It is very difficult to assume that all THREE pilots could miss the very possibility of stall, regardless of their training and practical experience. One, yes, but all three, no. However, if you are sure that you have forward speed, there is no stall, so that neatly explains both facts. If it is really true that they tried other things, but stubbornly insisted without changing only on that one action, than that is what all three of them believed.