What were the historical conditions that led to object oriented programming becoming a major programming paradigm?

Question

What were some of the economic (and other historical) factors that led to object oriented programming languages becoming influential? I know that Simula started things off, but was the adoption of OOP languages due to the ever increasing needs of business? Or, was the adoption due more to the new things that could be done with OOP languages?

Edit I'm really most interested in whether there was some factors going on external to the languages themselves that allowed for them to take hold.