I guess that's the main part, the Stanford founders I met (mostly second-hand, via friends who did work for them) seemed to have access to connections and surprisingly large amounts of "friends & family" seed funding. Maybe they were doing a ton of work behind the scenes to get it, but from my perspective it seemed like some pretty surprising piles of money accessible to pretty unproven companies (piles of money much larger than YC gives). My friends got decent pay out of it (even if below-market), so I'm not particularly bitter about it, but it was sort of an eye-opening "wow, people have friends/family who can kick in $750k just like that?" kind of moment.
Also quite different compared to the vibe around other vaguely nearby universities: Santa Clara University, UC Davis, UC Santa Cruz, UC Berkeley, Cal Poly SLO, etc. They all come across as more "working class", socially, which contrary to what I might've thought some years ago, seems to correlate against being startuppy. The working-class Cal-Poly/Santa-Clara/etc kids seemed mainly interested in getting a stable job with a big tech company, while the upper-class-background Stanford kids were all into startups.
The datapoint in your last paragraph fits well with the pro-social safety net sentiment that is sometimes expressed here: It is much easier to take the risk of creating a startup if you have a guaranteed safety net.
Kids from a genuinely rich family - as in, pitching in 750k is not a problem rich - are more likely to feel safe enough to take startup-related risks.
Also quite different compared to the vibe around other vaguely nearby universities: Santa Clara University, UC Davis, UC Santa Cruz, UC Berkeley, Cal Poly SLO, etc. They all come across as more "working class", socially, which contrary to what I might've thought some years ago, seems to correlate against being startuppy. The working-class Cal-Poly/Santa-Clara/etc kids seemed mainly interested in getting a stable job with a big tech company, while the upper-class-background Stanford kids were all into startups.