So if this isn't a new idea, then it shouldn't be worthy of Nobel prize.
It's a new idea in Bangladesh and much of the 3rd world. Additionally, this is the first time microcredit has been organized with the express purpose of boosting development.
The whole concept of microcredit is a old idea but redone, or innovated to a higher degree with extrodinary results.
FWIW, even before this great land was founded, the concept of loans, and banking had been around and used to produce financing, but never as such a small level and never in these parts of the world....and microcredit is a pretty new term.
Also, keep in mind, that being a "new idea" is not nor has ever been criteria for winning a nobel prize which is why every now and then you will see the unusual, where someone wins a prize for something that is either a further application, or improvement, a bigger extention of something else, and yet that something else never has won the award.
John Nash got his noble prize for his game theory, but by the time he got it, several folks has won awards for work based on using game theory and its applications before Nash won his.