In what way it is more successful? Both TIOBE and Redmonk don't confirm your thoughts.
http://sogrady-media.redmonk.com/sogrady/files/2015/07/lang-...
http://www.tiobe.com/index.php/content/paperinfo/tpci/index....
Dart arrived with much fanfare though, whereas TypeScript was more low-key, and it's taken a while to become mainstream. Google's announcement that Angular 2 would use it has brought it a lot more attention from outside of the traditional MS/.NET dev crowd.
Microsoft have also been shifting the project's focus towards a more Babel-esque one, emphasising greater interoperability with existing (untyped) JS libraries, and support for new ES6/2015 features (and beyond).
1. https://channel9.msdn.com/Shows/Going+Deep/Anders-Hejlsberg-...