Most companies don't even know that these are programming languages. Also don't assume people interested in these languages are "the best". Regarding JS, this is all hearsay, but I think nowadays they hire good profiles (competitive programmers / olympiad winner / top graduates from prestigious schools), ask them hard leetcode questions, and teach them OCaml (which anybody can learn, not particularly hard. Their talent pool isn't restricted to the OCaml community, as it used to be when they were less famous, except for niche use case (compiler work and so on...)