The question remains about Rashi’s explanation. In truth, even according to Rashi, Moshe is not really acting out of desperation but from strength. There is a term in cognitive psychology and negotiation theory known as “dislocation of expectations.” Sometimes the best approach one can take is doing the opposite of what your opponent is expecting. We can imagine that Bnei Yisrael and Korach expected Moshe to do two things. The first: to immediately intercede on Bnei Yisrael’s behalf with G-d, the second: counter Korach’s statements and arguments. However, Moshe realized that the situation was too volatile and dangerous for normal responses. Instead he falls to the ground, allowing the nation to hear his concern that this time they are beyond help. The impact on Bnei Yisrael must have been electrifying. In fact, very few people actively join the rebellion following Moshe’s response. They got the message.
Likewise, far from elevating Korach’s arguments to a level of legitimacy, Moshe skips straight to the testing stage. He challenges Korach without granting him any credibility. He lets Korach know from the outset that he is engaging Moshe in a zero-sum game. For various self-delusional reasons Korach accepts.
Thus, even according to Rashi, Moshe did not fall to the ground in an act of desperation but rather as part of a divinely inspired carefully thought out strategy. Far from violating the leadership rule of exuding confidence, Moshe’s actions exhibited his total control and firm belief that righteousness would prevail.