The only thing I think is outside both of these elements - product quality and viable strategy - is the component of luck be it right place, right time, or catching an unforeseen wave of buzz. The most well known success stories typically owe a non-insignificant amount of debt to good fortune out of the control of the product or strategy. It's a real elephant in the room and it's difficult for ego to acknowledge either in success or failure, but it's real.