I make the argument elsewhere that people attribute to credentials what they ought to be attributing to character (and luck, as you point out--and some talent, of course). My unprovable claim is that someone who is going to succeed probably doesn't need a degree or a university to do it.
I emphasize character here because it is my observation that this is the #1 reason people succeed or fail. It's not about being smart, though that can help with some things (and presents obstacles in other respects). I drilled this into my now-grown kids, one of whom is fairly smart but with other strong talents and the other who is probably even smarter than me: all that talent doesn't mean anything if you don't apply yourself with integrity and energy. I've had successful business owner bosses who were a lot "dumber" than me but whose work ethics, self-discipline, and wisdom put younger me to shame. I learned from them and succeeded in turn.
It's also worth pointing out that what a lot of people end up doing with their lives makes the financial and especially the opportunity costs of 4 years at a university a colossal waste. We see their collective opinion in the survey in TFA: nearly half don't think it was worth it, which is a truly terrible commentary.