it's touch and, um, "go" whether a Google language will gain popularity outside the company itself. The world did not rush to embrace Dart for example, outside the narrow remit of Flutter app development.

Go somehow become successful.

Yes, Dart would have been a dead language without flutter framework

I think Go became successful because it filled a niche: people wanted a simple language that was performant and useful for building APIs and network applications, while being easy to learn, particularly for new developers (Go has shortcomings, but I can understand the reasons for its appeal).

Dart on the other hand seems like a JS competitor that, in a world where Typescript exists, does not have a rationale other than the framework it was built for.

I mean, the niche you describe was IMHO filled just as well by Java.

Java is definitely not the be all and end all in this space, I especially feel like it has fallen out of time quite a bit, but Go hasn't exactly moved forward from 70s either...
@AstraKernel

I think Go was intended to be "dumb language we can throw at the 1000 new graduates we induct every year" which is both its appeal and its frustration.

That might explain why it seems so dated - it eschews anything more complex that might have come along in the past few decades (other than async etc).