I think dart/flutter serves primarily two purposes, as I see it. First the obvious one, Google is trying to get devs used to flutter as when the time comes to switch to Fuchsia/Zircon, it would be relatively a breeze.
Secondly, and the most immediate reason, I think it's a very clever and clear move from Google to lock-in devs into using Google Cloud services like Firebase and Cloud ML services by leveraging Flutter. If you have observed, Microsoft has given a rebirth to their Xamarin developers YouTube channel and have been hosting 'The Xamarin Show', which is, hmm, quite similar to 'The Boring Flutter Development Show'.
Besides Dart v1.0, Dartium, Angular Dart when they were still relevant to Chrome and Angular teams, and following up on Flutter?
I usually only criticize stuff that I actually have some level of experience with.
AdWords team rescued Flutter, after Chrome and Angular teams stop caring, which even caused Dart designers like Gilad to leave in disagreement.
I believe that they found out some internal management support that is willing to give them a time frame, of lets say 5 years to prove themselves worthy of such support.
Android has more political power ChromeOS has adopted Android and not the other way around, the two commercial OSes from Google.
While their experimental OS, Fuchsia is now adding support to run ART, while at the same time via Scenic, decoupling themselves from the UI framework.
You want to believe in Dart/Flutter, go for it.
Me, I am betting it will be joining the list of abandoned Google projects in a couple of years.