I think it's always a mix of things which lead to the success of any language ecosystem. I think Go has at least 3 things going for it:

   1. It got the *initial push* from its Google pedigree which allowed it to gain attention and traction

   2. It meets the *merit threshold* so that when people gave it a try, they wanted to continue using it

   3. It had a good *product market fit*: in the world where Go was released, *a lot* of server-side software was being written in scripting languages and there was a clear value proposition for a fast, compiled, statically typed language with good tooling for handing server work.

I think Dart fell down on that third point. Front-end development is very different from back-end, and people already had toolsets they were familiar with based in Javascript. Switching to Dart would have meant throwing out all these separate inter-operable tools and betting on a new paradigm.

I think that's why something like React or Typescript could really explode in that space: they could be added incrementally to a project while still keeping most things familiar.