A reader writes:
The real question is not why was Mickey more popular than Bugs, which pretty much follows the early American cultural preference for mischievous but safe Tom Sawyer types over the "All right, I'll go to hell" Huck Finn types.
The real question is: Why did Mickey have to wear pants but Donald Duck didn't?
I know I'm probably not original in this, but when I was growing up I saw Bugs Bunny a symbol of immense power. Here was a guy who could do anything. I admired him greatly.
When I got older and studied a little mythology in more depth, I realized that Bugs Bunny was Pan, another little guy who was really, well, everything ("pan" means "everything" in Greek). He made fools of bullies and blowhards, and that suited me just fine. You knew just at the moment when the fools thought they had captured him or humiliated him he could produce a lit stick of dynamite.
I wanted to do that.
There's a simple explanation for why Mickey Mouse is more popular than Bugs Bunny. Mickey is happy, while Bugs is cynical. Happiness beats cynicism every time.