While I believe this (the luck part), I'm not sure most startup folks do. Or, there is at least some severe cognitive dissonance going on when they begin to discover it.
Even "the pivot" itself was made popular by The Lean Startup–the book that many take as the formula for startup success (very much the antithesis of luck).
Yes, you have to hustle. Yes, you have to build something people want. Yes, you should have an awesome team. When you combine all those things and still fail, most people will blame something besides just luck. ("I couldn't get funding", "Google changed their algorithm", "I couldn't hire the right person for X")
Of course, when a 9-figure exit happens to someone who can't code as good as you and didn't go to as good a school as you–then it was most definitely luck.