When Korach first challenges Moshe, Moshe is unable to respond – he falls on his face. Why?
Is it possible that Moshe cannot believe that anyone would want his job?!
Moshe’s work was incredibly difficult. He had to constantly interact with Almighty G-d. And at the very same time, Moshe was supposed to lead and educate and manage an unruly, ungrateful, needy, and persistently stubborn people. Somehow Moshe was supposed to create a connection between these two incompatible forces, to keep both sides from walking away (despite the repeated desire by both G-d and the people to do just that).
On top of all of this, Moshe was not able to have a normal marriage or family. Nor, despite all his efforts, was Moshe ever praised by the people; they only criticized or complained. Did we mention that they were ungrateful?
What kind of a fool would want Moshe’s job?
So when Korach makes his play for power, Moshe is speechless. He falls on his face.
But then Moshe gets up. Because he realizes that Korach does not actually want Moshe’s job – he does not want to be Moshe. Instead, Korach aims for a much more pedestrian form of power: he wants to be In Charge. To Korach, this surely looked more like a Pharoanic kind of role than Moshe’s service.
Because Korach does not actually understand the nature of the job – let alone be able to meet its requirements – Moshe does not stand down. For the sake of G-d’s interests – and those of the people as well – Moshe fights off the leadership challenge.