We often start with the null hypothesis of artistic "exceptionalism, which imagines him [or her] as a freak of isolated genius", i.e., we assume that the credited creator worked alone.
I think that's wrong and few serious human endeavors are accomplished alone. In the arts, look at stories about how works were really created. Pop music is an easy example because it's well known: Songs are written with a suggestion from a friend, input from the producer, are based on something the performer heard on the train, are created when someone uncredited sits in on the session and provides the key hook, etc. A friend is writing a book, and I spent hours reading it and offering suggestions; I'll receive no credit (and I don't want or deserve it). In the code people write, how much is done without any help from others, without using existing code and ideas? As the saying goes, good artists borrow; great artists steal.