Credit Card

The Shape of the Credit Card

Here's a question that is bugging me and I can't find a satisfying answer.

Who designed the shape of the credit card? And why is it exactly this shape that became almost the omnipresent, universal type of card?

I know, that it's shape is standardized by the norm ISO/IEC 7810. I also know, that the shape is pretty similar to the size of business cards in certain countries. So maybe, the shape was adopted by the already common medium. But that would lead to the question, why the business card is shaped the way it is. But maybe I'm going the wrong direction here.

I thought this forum might be a good place to search for answers. Any ideas?