EDIT: Wilfred IS the original author [3]; my apologies.
Not to discredit Wilfred (it looks like he's taken over the project as the maintainer), but, based on the historical contributions [1], it looks like it was originally developed by Max Brunsfeld, who also created Tree-sitter. [2]
I think the contributor graph is misleading, and that he's using git-subtree to vendor tree-sitter, which makes it look like others have contributed more to the project.