Getting a DnD group together is like assembling the Avengers. You each have your own role, but you’re all equally important. Okay, the DM is a little bit more important. They’re kind of like the Nicky Fury of the operation. They’re sort of in charge, but they’re also the shadowy figure that exists behind a partition. The DM has the important job of doling out information piece by piece while also maintaining an air of mystery. If they wear their heart on their sleeve too much, then stuff will be revealed before it’s time. 

If they’re too mysterious, then the players won’t have anything to work with. They also have to set the right tone for the campaign. They have to make sure it’s fun, but not so fun that it gets out of hand and rules start being broken. They have to set the pace, and they’re hopefully pretty good at doing dumb character voices.