First, we had BuckleScript, that compiled OCaml to JavaScript to bring the OCaml type system to the Web.
Then we had Reason, that brought JS syntax to OCaml, so it's easier to grasp for JS devs.
Seemingly, some people didn't care about OCaml at all, and forked (I guess?) Reason to ReScript, that focused on JS compilation. They also added a few syntax changes in the process.
Now, the remaining (pre-fork) Reason people created a new(?) compiler that's an alternative to BuckleScript, and compiles OCaml and Reason to JS.
While I appreciate the effort, and think ReScript and Reason are superior to TypeScript, I totally understand why it didn't get as popular as this superiority implies.