Musar על מגילה 37:5

In Megillah 19 we find an argument as to how much of the Megillah has to be read. Four views are mentioned as we have already stated earlier. The views are based on whether תקפו של אחשורוש, or תקפו של מרדכי, or תקפו של המן, or תקפו של נס i.e. the power of Ahasverus, Haman, Mordechai or the extent of the miracle, determines from which point the story has to be read in order to fulfil the commandment. The view mentioned last, that of Rabbi Shimon bar Yochai, states that the extent of the miracle is what determines from which part of the Megillah one has to start reading. Why would his colleagues of the Mishnah disagree with such a viewpoint?