“Every one of them has a different understanding of what he said and meant.”
That is because he paskened differently to different people in different circumstances, and at times changed his mind on things. Any decent rav will do that; kal v’chomer the Gedol HaDor.
And he *was* the Gedol HaDor for the United States for two generations. His students ended up leading most of the orthodox synagogues in America. He isn’t studied in charedi yeshivot today because he hardly published anything during his lifetime and few charedi yeshiva teachers are linked directly to his mesorah.