They used to be quite a niche trading company, known in the functional language community for their use of OCaml. But they grew to one of the highest paying company in the world.
Most recently due to FTX leadership being Jane Street alumni but they get mentioned a lot here due to OCaml.
Jane Street did outreaches at MIT (dunno which other schools), wrote blog-like things, used an exotic language, paid a lot of money (word gets around), etc.
They've been on radar forever, but I used to work in finance and like Ocaml.
Jane Street is huge in HFT space. SBF started at Jane Street.
I work in the HFT space. Jane Street in not an HFT, they are not trading in a very latency sensitive asset class.