Me explaining to my friend who’s been at Jump for 20 years how to predict a 5-second return with a volume-weighted midprice.

One of the biggest problems with hiring B-class players is that high-quality research and discussions require absolute trust among the people in the room. Unfortunately, A-players will quickly identify the weakest links and lose trust — even when the idea itself is good. In debates, we rely heavily on the reputation and trustworthiness of the participants. There’s a huge difference between hearing the sentence “I think this conclusion is wrong” from an A-player versus hearing it from a B-player. That’s another reason why it’s so important to focus on hiring great people.

You definitely don't need to be a gold medalist of IMO to be a great quant, but also don't be fooled by this quote. It's the quote of someone that graduated from MIT, finished PhD at the age of 23 and gave non-trivial proofs for Differential Geometry in his 20s. If he said that he was not the fastest guy or did not well in Olympiad it does not mean that he was stupid - he was a really, really smart person, way above most of us here.