here's the thing, _I don't think ReasonML is dead_! I've tried to dig for more clarity in the GitHub issue trackers and come up with mostly nothing. I am starting to get the feeling there is some kind of dispute or falling out between the maintainers of the two projects.
ReasonML isn't dead, but the way I heard the story it has always been a spare time project not a properly funded FB team. There was just enough spare time early on to get the community excited.
From the same source, I heard ReScript does have funding behind it.
Maybe they simply disagreed about the syntax...
This was my exact path. A friend and I wanted to make a small SaaS using Reason for the backend, because it smoothed out a bunch of what we considered were "rough edges" in OCaml. Then the ReScript split happened, and we realised that Reason was dead for all intents and purposes. It's hard to imagine the Reason team will continue updating Reason when they're focusing hard on ReScript instead.