While it's true he will give grants to accomplished people, he also makes far more grants to smart young people (often from non-Western, lower income nations) that are _not_ accomplished, for things like "general career development". People like Byrne Hobart and David Perell launched their writing careers via EM. And even in the list you linked to, there's a 15 year old and a high school junior.

Regarding success rate, his explicit goal is to fund extremely ambitious people and projects that would otherwise struggle or not get funding at all. This could mean funding the most speculative or risky (or highly societally beneficial but lower financial return) ideas from already accomplished people or funding talented people that would struggle to get funding otherwise (due to age, access to capital, etc). I believe (and I think TC agrees) that there are likely many people and projects whose course could be substantially altered for the better if given access to a reasonably small amount of money early enough to convince the person to work on it full time.