Plus, I believe at the time there was some core Chrome developers Google wanted to retain and keep busy with developing Flutter.

These are all cool projects, and there are hardly any companies developing actual operating systems nowadays. It would be sad to see it go, but on the otherhand, I haven't seen folks outside of Google use this OS despite its strengths, and perhaps that's the real problem

This, BTW, is why the entire FOSS world was shitting itself over the Oracle lawsuit. If they were to win, it'd trigger a cascade of other companies claiming interface copyright over every competing OS and library that has a similar interface but is not entirely a compatible reimplementation[0]. The problem is that programmers thought interfaces weren't copyrightable and thus have been doing the whole "embrace and extend" dance for decades. Think less WINE and more GNU: something that's very explicitly Not UNIX, is sorta-kinda compatible enough with it, but also has a lot of its own weird extensions. That's what Oracle thought shouldn't be allowed.

Fuschia replaces things lower level than the Java APIs - things Oracle doesn't own. That's the Linux kernel and a good chunk of Android userland[1]. If, say, SCO were to somehow come back from the dead with some new bullshit legal claim to the Linux kernel, then yeah, Fuschia could get Google out of that kind of a jam. But that isn't the case right now.

[0] Existing Ninth Circuit[2] precedent regarding, of all things, PS1 emulation, precludes suing over compatible reimplementations of existing interfaces. The problem with Android was that it wasn't compatible; they'd taken some but not all of the Java APIs, which was against Sun policy. Sun didn't want partial implementations or extensions in the wild. In fact, Sun had already successfully sued and won against Microsoft for shipping MSJVM with COM bindings.

[1] Which, funnily enough, contains no GNU code so you can't call it GNU/Android.

[2] Yes, the lawsuit was in the Federal Circuit, not the Ninth Circuit.

And Fuschia+Dart+Flutter runs perfectly fine. There's nothing wrong with them. Should Google keep pouring money into them? YES. Absolutely yes. But do they need 500+ people on each project? Probably not. Remember Google has on the order of 100,000 software engineers.

I'm guessing nowadays Kotlin plays this role? Its multi-platform nature means that the Android world can eventually be detached from the JVM backend, if I understand correctly.

Even with ART, Kotlin withouth the richness of the Java ecosystem at Maven Central is worthless, hence why after the whole Kotlin push, now ART is modular and updated to more recent versions, currently Java 17 LTS. Via Play Store updates from Android 12 onwards.

Kotlin was pushed by a couple of folks with managment powers, given the team marriage with JetBrains, and a way to push common interests with Android tooling.

Why do you think Kotlin MP would contribute to JetBrains' bottom line when at the same time you think Flutter does NOT contribute enough to Google's?

I get it, Google's bottom line is on another level, but at the same time, if someone can afford to invest on technologies that do not bring in any profit, that's Google if it thinks it increases its reach, which Flutter/Dart do in a way that Kotlin cannot, given Google controls them but not Kotlin (though you could make a case Google effectively controls Kotlin, at least somewhat?).

That said, building a really good cross platform UI toolkit and framework is really hard. It remains to be seen if JetBrains can pull it off.

one codebase to cover web, android, iOS and desktop apps.

and for that simple reason, flutter won't go away. no other UI development framework comes close to the productivity of flutter.

Personally I think it's a lost cause; every few years they change direction in hopes of finding a concrete use case that doesn't displace some existing Google project. The Nest was Fuchsia's greatest achievement and even that was held together with strings and glue behind the scenes.