There was a complete fork to support it, Dartium.

https://chromium.googlesource.com/dart/dartium/src/

Dart is only around because it was rescued by AdWords team, which had just migrated from GWT into AngularDart, and wasn't happy to do yet another transition.

Most of the key names from Smalltalk/Self background that were part of Dart 1.0 left the team at this point.

It managed to stay around long enough to get the attention of the Flutter team, originally their prototype was done in JavaScript, which is also the reason why Dart 2.0 was a complete reboot of its type system, from dynamically typed with optional typing, to strongly typed language with type inference.

And it isn't as if Flutter is a great success, Fuchsia never made it big, the Android team counter attacked with Kotlin's adoption, JetPack Compose, and Kotlin Multiplatform.