You confuse two different things.
The question being asked is whether grit is the one trait to rule them all.
My answer to that is no it's not because most people who are successful have grit (but far from all) and many people who have grit are not successful.
And so I introduce another element, luck. Luck is as you say not something you can count on which is the very point here and actually proves both my point but introduces another important one.
You can't copy someone for success. It's not just a matter of having grit it's a matter of being lucky and having grit.
I don't know of any rule or law that implies that something can only be true if you can count on it.
A lottery winner who might keep playing again and again and one day win the lottery have grit but it's still luck if they win.
That's not the question I was addressing. I was addressing the extent to which one can attribute someone's success to "luck", and I argue that both grit AND luck can matter to one's outcomes.
A lottery winner who might keep playing again and again and one day win the lottery have grit but it's still luck if they win.
That's not even remotely relevant, as a lottery is very specifically a game of chance. Life involves an element of things you can't control, but it also involves a lot of things you can.
The lottery winners ability to buy the ticket to begin with is part of life. So yes it's actually relevant.
Now, you might ask, "well, what if the DOS thing didn't happen?" And the thing is, we'll never know, because it did happen. But if you believe that gates, ballmer, allen, etc. were smart, hard-working and talented, it seems likely they would still have ultimately been "successful" in some fashion, even if the story unfolded quite differently.
Luck and network are the single most defining factors of why some are successful
I don't know if we'll ever be able to actually quantify and measure that, but my suspicion is that grit/perserverance/will are at least as important as luck and/or network.
But keep in mind, there are many levels of "success". Life isn't as binary as "wound up homeless and sleeping in a gutter" vs. "wound up a billionaire CEO".