You're right, and it's relevant to the narrative. Thiel jumped into finance from a legal career, which can be difficult to do unless you capitalize on a market shift (e.g. bankruptcy lawyers jumping to distressed asset funds in the most recent recession). Derivatives was a growing area in the early 1990's, which presumably made it easier for him. Which was fortuitous, because since he didn't come from money, he might not have been in a position to start his first fund without his Wall Street connections.
This aspect of finance, the difficulty of getting into the field later on in one's career, is a major reason why so many Ivy-leaugers pursue it right out of school.
I agree it's relevant, but not because it supports the argument. While investment banking is, at least today, seen as prestigious and a pathway to executive management, trading is viewed as boarish and generally does not carry over to anything outside of trading. So Thiel may have gained access to capital from connections he made in finance but not substantial leadership-related prestige.
(Also I don't think jumping from super-elite-law to finance is particularly difficult, it seems pretty common).
My point is that Thiel probably wouldn't have been able to raise a million dollars to start his own fund if he hadn't worked at Credit Suisse, and it wasn't a "gimme" for him to get that job having started outside of finance originally. That's relevant to any entrepreneurial Ivy-student who contemplates starting his career outside of finance or consulting.
I agree with you, I just wanted to make the important distinction between investment banking and trading careers, which are often conflated. The difference isn't whether trading is as hard to get into but what are the "exit ops" and how they compare to those in IB. Trading has few, investment banking has many, especially in business-analyst/management-track roles in industry. The upshot of trading is that it is potentially more lucrative.
This aspect of finance, the difficulty of getting into the field later on in one's career, is a major reason why so many Ivy-leaugers pursue it right out of school.