I think this is slightly uncharitable. The people working on BuckleScript had been unhappy about syntax for a while, and wanted to make it simpler for people coming from JS. They also kept supporting Reason syntax - it's quite literally in the announcement and forum threads from the time that old code will continue to work.
I can't speak to why the rebrand went down the way it did, as none of us can know for sure, but I think it might have more to do with internal communication between team members than any one person taking their toys and going home, so to speak.
> I mean, the way that the creator of ReScript behaved on discord to any criticism to his decisions at the time didn't helped
I didn't hang around on the Reason discord (for good reason, I now suppose :P) but I don't think that had anything to do with Reason dying out. No matter how the ReScript people behaved, Reason native could've gone its own way, but it didn't, and the responsibility for that is on Reason. As much responsibility as there is, ofc. I don't mean to imply that the team behind Reason should've continued developing if they didn't want to, I just don't think the ReScript people should be held to account for how Reason evolved.
(FWIW, I was interested in Reason only for native, and have zero interest in ReScript, so I say this as someone who is "on your side".)