Angular failed? :D really?
There are not many languages out there which reached a broad adoption within a short time. There isn’t even an version 2.0 yet of Dart.
There were times where there were big gaps for new languages to fill, like when Java was introduced and it still didn’t have broad adoption after 5 years on the market.
Others like C# or Swift which were the only well supported option from companies with big markets they dominated had it even easier and still took years to get broad adoption.
Dart is competing with many established languages and has no way to be “forced” onto developers like other languages. Google doesn’t even force it on its own teams, still the Flutter team decided to use it.
In this difficult environment Dart is doing great.