Before Moshe Rabbenu, the only Torah was the seven mitzvos of Noach's sons. Moshe succeeded in removing the Torah from a bigger klipa than it was before, but it was only a partial success. The Torah that he left us with, the Second Tablets, was a greater Torah than what the world had known before. He could not carry it to its fullest aspect because of the sin of the Golden Calf and the internalness of the Torah itself was missing. The main argument that Moshe had with G-d was the descration of G-d's Name when it came to saving them after the sin of the Golden Calf. The nations of the world would claim that G-d didn't have the ability to bring them to the Land of Israel and therefore destroyed them in the desert. Destroying Klal Yisrael in the desert would show that there are two authorities, G-d forbid, and that G-d didn't have the power to have mercy on them. Allowing Klal Yisrael to be saved whether or not they were meritorious would reveal G-d's oneness in a much greater way than their destruction and the subsequent creation of a new nation.