I'm not sure that Rust is there yet either mind you, but give it time, perhaps it will...
"Web development" is a grueling land war that requires massive investment in foundational libraries and fairly sophisticated tooling just to do a modern "hello world" app. Any language/platform that isn't explicitly dedicated to "web development" will always be lagging many generations behind those that do (i.e. rails and waves hands javascript).
I agree with the sentiment that Rust and OCaml aren't really peers. More generally, the urge to transition to Rust in general application development is as puzzling to me as it is to your parent here: it has unique benefits for systems programming, but that absolutely carries costs for a ton of non-systems contexts where you could just as easily use OCaml, or (modern) Java, or ...
They didn't have aggressive marketing or zealous community.
They didn't have massive influx from ruby rails or javascript webshit crowds.