As someone else mentioned, they had to rename due to legal concerns over trademarks. If people start abandoning Terraform for this alternative, Hashicorp will look for any reason to sue.
I totally agree that. But I suppose that with this rebranding they are looking for moving away the original project as much as possible.
I'm not sure if this movement has a lot of sense right now because by when the project had finally been released it will still being a fork of the original Terraform, but they may change this in a near future.