I don't care who agreed to what, it's bad engineering practice to take a working successfully launched product and throw out its entire working software stack no matter how inelegant it seems. To what end? What did Fuchsia offer? When it finally shipped -- what, 2, 3 years late? --- custmers couldn't even tell it happened.
And in order to make it happen it also required writing the already-launched HTML-based UI in Flutter/Dart. Again ... why? What for? There wasn't even a working "native" Flutter at the time, despite promises, and there certainly wasn't a working accessibility stack -- no screen reader, no magnification, nothing -- so that all had to be kludged in. It was everything wrong with the "rewrites considered harmful" distilled.
Not to mention terrible for morale, execution, planning, budget, customer satisfaction.
I was just a lowly SWE 3 "IC" just in the trenches, not nearly as "important" as all that, so my opinion mattered not at all. But to me it violated every sound engineering / project planning principle I'd learned in the 15 years of my career up to that point. Just another event that led to me becoming quite cynical about the ability of leadership at Google to actually manage anything of significant complexity that wasn't ads/search related.
Again, Fuchsia .. very neat. But it didn't belong there.