Why was credit invented?
Credit was invented in order to allow people to get the value of some service/good immediately while providing a legal means to pay for that item/service over time.
In the US, Singer was the first to provide installment credit for the purchase of sewing machines.
Credit card debt was not exactly invented by anyone. However, the idea of a revolving credit was established in the 19th century. It was not until 1950 that Frank McNamara, head of the Hamilton Credit Corporation and members of the Bloomingdale family (founders of the Bloomingdale stores) created the Diners Club card.