Not sole credit for the whole project, just saying that one person came up with the idea, breakthrough, formula, etc...

Maybe Apple is a good modern example. Steve Jobs doesn't deserve sole credit for the company, he doesn't even deserve sole credit for any of their products, but one day he made a set of breakthroughs or decisions that other people built upon which led to new products that wouldn't exist if he weren't there.

Again, no question other people were involved and were important players in building on those breakthrough ideas, but I think Steinbeck's point is that the task of going from 0 to 1 requires an individual to make a breakthrough, not a committee.