Rashi explains that while the face of Moshe was comparable to the sun, the face of Yehoshua wasn’t quite as great and was similar only to the moon. On this, the Gemora in Bava Basra (75a) adds that upon recognizing this, the elders of the generation remarked oy la l’osah busha, oy la l’osah k’limah – woe to us for this humiliation. It is difficult to understand why they only felt shamed upon noting this distinction, and why specifically Yehoshua made them feel this way and not the even greater Moshe.
Rav Itzele Volozhiner and the Chofetz Chaim compare this to a case of a rich businessman who arrives one day in a small rural village, asking if anybody would be interested in becoming his partner in a new project. The businessman offered to put up all of the necessary funds and expertise, but merely desired a hard worker to assist him with managing and running the business. Most of the residents were content with their simple lifestyles and were skeptical about the man’s promises of fame and fortune, so they passed on the offer. One simple, illiterate villager decided that he had nothing to lose, and agreed to become the man’s partner. A few years later, the pair returned to visit the village, arriving in an impressive carriage and dressed in a manner which clearly revealed the success of their project. At this sight, the villagers were mortified and ran to hide.
They explained that they weren’t embarrassed by the wealthy entrepreneur, as they felt that his education and resources gave him advantages that they could only dream of. They were, however, quite shamed at the sight of the success and riches which had met their former neighbor, as they remembered all too well that they had been offered the same opportunity as he, but only he was wise enough to take advantage of it. The recognition of what they had had the ability to become and their failure to do so generated powerful feelings of humiliation.
Similarly, the Jews in the wilderness never measured themselves against the levels reached by Moshe, as they viewed the pious family into which he was born and the elevated soul with which he was blessed (as he lit up the house with light upon his birth) as bestowing upon him opportunities for greatness that they could never fathom. On the other hand, Rav Yehuda Zev Segal, the Manchester Rosh Yeshiva, notes that Yehoshua was neither the wisest nor the greatest of the generation. The Ramban (13:4) writes that the spies are listed in descending order of greatness, which means that Yehoshua was only 5th out of the 12 spies. The Baal HaTurim (13:3) writes that each of the spies was only a leader of 50 Jews, meaning that there were many greater Jews who led groups of 100 or even 1000.
Rather, Rashi explains (27:16) that Yehoshua was chosen on the basis of his devoted service of Moshe throughout the 40 years in the desert. Upon recognizing this, the Jews became aware of the levels which could be reached when a person who had been just like them used his talents to their fullest. The Vilna Gaon writes that the most excruciatingly painful experience a person goes through after his death is when he is shown a picture of what he was capable of and destined to become had he maximized his potential, which will stand in stark contrast to what he actually accomplished, and it was this humiliation that the Jews experienced upon the inauguration of Yehoshua as Moshe’s successor.
