The first time was hearing about a startup that used OCaml on one of the monthly hackernews Who is hiring thread. The current day job was also somewhat similar in that I had read about a startup's job listing on the OCaml forum [1], checked with them again a while later (the startup was acquired by another company), and found an open role on the team that continued to use OCaml after the acquisition.
> it but it seems like there are very very few jobs that use it primarily.
I completely agree. I never tried looking for an OCaml job mostly because there weren't enough options at-least in the US (I'm based in USA), and I am picky about who I work for and wasn't interested in exploring job opportunities at companies working on cryptocurrencies. I just got lucky that I stumbled upon two different companies that used OCaml. The first time around I applied for the job because of OCaml, the second time around it was because I liked the company and OCaml was an added bonus on top.