It's not religious to observe that founders who made a successful exit are well-poised to do it again.
They're swimming in money, they have a bunch of investors in their phone contacts, and they know all the ins and outs from the last time they put a startup through its life cycle. How could they not be in better shape than some kid slurping ramen in his first YC cohort?
This does leave two big wildcards: the idea (specifically its product-market fit) and pure dumb luck. From what you wrote, I'm guessing that you think this isn't realized by the "cult of YC" as well as it should be, whereas I guess differently, but it doesn't matter that much. We all recognize that it's there, and without those two ingredients you can't succeed.
As an aside, I've seen two different kinds of 'luck' come up in these kinds of conversations: the sort I'm referring to above, and the sundry genetic and social inheritances to which a person is heir.
They're both valid uses of the word, I think the first is more obviously lucky than the latter. It is luck of a sort that someone is 2 meters tall, but I bet their parents were also taller than average, so saying that it's lucky that they were able to be a pro at basketball is going to confuse some people. There was no "them" before the peculiar genetic combination which conceived them, and after that, we're talking about some favorable circumstances (adequate time, a court, no crippling car accidents or stray bullets) and a great deal of hard work.
Similarly, you can call it luck that Jeff Bezos was able to borrow a quarter million from his family, or that Elon Musk apparently can sleep for four hours and work for twenty, constantly, for decades (a genetic quirk no less special and rare than being two meters tall): but you can call it fate as well.