It helps that GraphQL has an actual spec, protocol, and defined schema and is intended to be shipped as a separate microservice that just implements your schema

It helps that GraphQL has an actual spec, protocol, and defined schema and is intended to be shipped as a separate microservice that just implements your schema according to the spec. REST is more "hodge podge of concepts" that you can hack on and pollute and misunderstand at will. I guess nothing will stop people from making Frankenstein schemas or poorly performing resolvers but at least the consumption is mostly uniform?