The researchers failed

In the last part of the book, ‘That which is and that which is not’, in the sense of combining research with the halakhic level (in the context of understanding the words of the Meiri about Gentiles), the rabbi argues that each level should be complete in itself – in the context of drawing conclusions for today, I completely understand that it does not matter what the reasons were that motivated the posek, but rather that one should refer to the substance of the arguments.
But Katz explains in his article the reasons that caused Meiri to rule as he did, and in explaining the Meiri’s behavior, I didn’t understand why it doesn’t make sense to say that if you can’t find a logical reason why someone didn’t follow through with his distinction to the end, it was probably caused by a psychological reason (or a decision not to completely uproot the thing)?? After all, this is an explanation of the person’s behavior (in this case, Meiri, but the rabbi doesn’t agree with this general approach of the study), and behavior (including halachic rulings) is certainly also influenced by psychological motives. So I didn’t understand why it was said that Katz (and the general approach of the researchers) fell into a lack of understanding on this issue? (The rabbi mentions in one of the lines there the assumption that no one does things without a sufficient philosophical basis for his words. Does the rabbi dispute the possibility of acting out of fear/concern/emotions of this or that kind – without a logical basis?)