I think he's intentionally focusing on the luck aspect because I think his audience (Princeton undergrads) is used to the first narrative. As sort of an outsider (I'm a graduate student here), I sometimes get the sense that a fair amount of undergrads here are a bit too self-important. Certainly there are many awesome, down-to-earth people here too, but there are also a lot of people who are caught up in the fact that they are Princeton students and that by itself perhaps makes them better than students of "lesser" schools. I think in particular, Lewis' last full paragraph should be the take away for these students. Yes, they are very gifted and they may deserve every bit of benefit that comes their way, but they should also remember that there is at least some part of that they didn't/can't control. Acknowledging and being humbled by that will go a long way in life.

As a Princeton '12 who saw the speech live, I entirely agree. I'd add that this was the Baccalaureate ceremony, which was historically the part of graduation that featured an extensive sermon... in other words, a part that is designed to be humbling in every respect.

It's a superlatively false narrative to image that "sense random opportunity" is the only (or even common) scenario and that "work your ass off" is its only response.

I don't think he is saying anything is "solely" anything else. Just that it's unlikely that #1 is the full explanation.