- Reason+BuckleScript was confusing at best, having two websites and different release schedules.
- Reason's goal is to be a 100% mapped syntax for OCaml. This does not mesh well with the goal of producing readable JS, so ReScript will probably end up as a subset of OCaml features.
- Reason syntax changes apparently caused grief when applied to BuckleScript. This one was never very clear, but regardless now that the syntax is in-house the ReScript team can be more responsive with it.
The problem with this transition is that it was dropped on the community in an unfinished state and BuckleScript was retired completely. The goals of the change are, I think, mostly reasonable.