They really don't, less than 5% of opam packages depend on Base and that's their bottom controversial dependency I'd say. Barely anyone's complaining about their work on the OCaml platform or less opinionated libraries. I admit the feeling that they do lingers, but having used OCaml in anger for a few years I think it's a non-issue.

What they do seem to control is the learning pipeline, as a newcomer you find yourself somewhat funneled to Base, Core, etc. I tried them for a while, but eventually understood I don't really need them.

But going way back while yeah the team at Google controlled the direction, there were some pretty significant contributions from outside to channels, garbage collection, and goroutines and scheduling..

(They are the same language)

Reason at least was an active collaboration between several projects in the OCaml space with some feedback into OCaml proper (even though there was a lot of initial resistance IIRC).