Then why do we have books on grit? And why is grit such a good indicator of successful founders?
The reason there are so many books on grit is because it's a very compelling lie that anyone can succeed if they just try hard enough without giving up. It's useful for the person who hasn't succeeded because it gives them hope. It's useful for the person who has succeeded because it implies that they earned/deserve what they have because they were better than others or tried harder than others did. These are lies, but they are comforting to a lot of people and so they sell a lot of books. Books that say things like "Be born to wealthy parents, preferably in a rich nation or your odds of success are highly unlikely, then also get really lucky" just aren't going to sell as well.
Based on what? Biographical accounts by successful founders?
Nassim Taleb's Fooled By Randomness [1] covers the topic of mis-attribution of some causal factor X (i.e. grit) to some phenomena (i.e. business success) that can be effectively explained solely by randomness. In the specific case of successfully starting a business, causal factors are often mis-attributed post-facto through a lens that blatantly ignores survivorship bias [2].