Theory: If people read conclusion first, then people tend to evaluate whether they agree or not after reading conclusion. Emotional reaction toward conclusion will bias interpretation of arguments.

The remaining arguments are more likely to be accepted or rejected based on what you know conclusion is. So instead of asking "is this true", people will start either with "I am looking for nitpick cause I see this is going toward bad conclusion" or with "yeah sure, it shows what I think".

However, they will still feel like they evaluated arguments on merit. If the conclusion is last, people can and some will go back to arguments to bias them, but it is easier to see what they are doing.