In the Golden Age, most of the villains required no particular reason for doing what they did. Why did the Joker use crimes involving humor? Because he was the Joker. Why the Penguin commit bird crimes, or the Catwoman crimes involving a cat? Because that's who they were.
Oh, sure, we learned a lot more about the characters as time went by. We discovered that the Joker had dived into a vat of chemicals, giving him his bizarre appearance and driving him nuts. And the Catwoman had amnesia, caused by a plane crash.
But in the Silver Age it no longer was possible to ignore an "origin" for costumed villains. Yet because of the very tight nature of the stories back then, the origin by definition had to be very brief.
And so the origins started to look very similar, particularly for Batman villains. The basic template was that the villain is mocked for something, and as a result, he goes a little cuckoo and starts using that something for crime.
Danny the Dummy: