Sure, Adwords migrated from GWT to Dart. (And eventually I followed.) At one point, Dart moved from the Chrome division to the Adwords division. And Adwords alone can fund a team to do developer tools for them. Then, Flutter came a bit later.
It's been over a decade since then, though, and I'm out of touch now.
In fact AdWords is the reason Dart was still around when Flutter came to be.
They still maintaining it's predecessor that the Google "core properties" ran on: Closure (not Clojure), the javascript compiler. It's an evolution of the hack that Gmail initially was built on.
So they're probably investing in it enough for basic maintenance, but don't really care about evolving the language.