The Hero Journey

Bilbo finds Thorin and tells them, don't tell the elf king anything. Because they're afraid the elf king will say, Oh, I'll let you go. But you have to give me some of the treasure. And then it says, they all trusted Bilbo. Perhaps that was part of his reason for going off and leaving them. In other words, why did Gandalf leave? Maybe part of the reason was so that Bilbo could become a hero.