After attending a pretigious "Dungeon Master School for Gifted Youngsters", the DM promptly flunked out and began selling steak knives and assorted cutlery door to door.
He was doing very badly.
One day, though, he got to a door and a frantic man who looked like Yoda after plastic surgery came out and began sobbing on his kneecap.
"Please!" he begged, "You gotta take over this game for me!
The Players are driving me NUTS!!!!"

The DM nodded, and has been leading it ever since.