The vast majority of professors, I'd say, are like that.
In startups, it seems that a strong ego is an advantage - if not a necessity (see: Elon Musk, Adam Neumann, Steve Jobs). There's an attitude (usually explicit, but sometimes implicit) of "we're disrupting the _____ industry and changing the world!".
Overall, I think you can find strong egos in any industry or job. However, my guess is that if you (somehow) ranked researchers and founders by ego, you'd find that the distributions were quite different. My guess is that the majority of founders have strong egos, with a long tail of those less ego-centric and that researchers would be quite the opposite - generally less ego-centric, with a long tail of strong-ego individuals.
The only group not included in "professors" is "postdocs" then, who are temporary staff who usually leave academia after a year or two.
Regardless, I'd say the definition of a "successful researcher" is usually someone who has become a professor.
Whilst there are many great postdocs, very few (any?) of the good ones become professors.
