Anyone can found a company with a $1 market cap and have full ownership from their one dollar investment. But it's meaningless unless they turn that into an actually valuable company with a market cap in the billions. Thiel just got exceptionally lucky, in addition to a bunch of hard and smart work.
I think this is a concept a lot of us struggle with when imagining the extreme wealth of the most elite tech entrepreneurs. Bezos, Gate, Zuck, and the rest all started with worthless companies and had substantial ownership as founders. Their wealth came from turning those large stakes in worthless companies into slightly smaller stakes into companies worth hundreds of billions.