If one wished to really delve into if a personality is responsible for a company's success, you could read a book called "Good to Great". A good fraction of the book covers why some companies continue to become "Great" after earlier leaders are gone. I'm sure I'm doing an injustice to the more nuanced concepts in the book, and this might be considered a "spoiler", but I recall the gist was that if there wasn't a strong culture that survived past the earlier leaders leaving, the continued success of the company was less assured. The book seemed scientific in it's selection and analysis of historical companies and came up with compelling thoughts on the factors that caused some to continue on to greatness, and others to flounder.