What's the point of using a different syntax if you are going to be interacting,reading,fixing code in ocaml syntax?
They lost the Flow-TypeScript battle. And they learned, they wanted even more typesafety I guess.
Since TypeScript also compiles to JS, bringing "something a little less like JS, but a lot more safe" to the table seemed a better idea that pushing "unfamiliar syntax, but heay, it compiles to JS"
If there is any battle, I predict will probably be between Flow and Reason inside the Facebook org because of competing solutions.
There's even a browser extension which converts OCaml syntax to ReasonML and vice versa in docs.