Dart was only created to be faster than JavaScript. Here's the leaked memo about why it was created: https://gist.github.com/paulmillr/1208618

tldr; JavaScript has "baggage" and can't be made any faster than it currently is, need a different VM + language with types.

Btw, the Dart creators are compiler engineers, not language designers. It explains a bit about why it has failed to catch on.