I can't dismiss Elons drive, ability to get his hands dirty, and many other characteristics. But the primary difference I see in this comparison is simply risk aversion. YC and their VCs are in it to make money by placing a number of small bets, knowing some will be losers. To go big like SpaceX requires you to be all in. Elon nearly went broke a couple times. He's willing to take that risk because he's in it for the results, not the money.
I used to wonder if it was just hype for employees and investors to say that SpaceX goal was to make humanity multi planetary. The last couple years have convinced me he's for real. The man could retire now. SpaceX could just own the launch industry by cutting cost for a while, or sit back and enjoy higher profits from reusability. But starship and mass production of it? Nonsense unless the stated mission is for real.
People can do so much more if it's about the mission and not the money, and that includes investors.