"Google" is actually a key differentiator here, because I think Google is uniquely focused on both design (it's been a long road to get here, but at this point I think Google is second only to Apple in design focus.) and interopability. Apple would _never_ make a cross-platform UI framework. What does this mean? Google's vast resources in design, development, & testing, equaled by very few, are behind this initiative. There's no doubt that is a competitive advantage.

The more interesting question is "Why does Flutter exist?" Google is, after all, a business. What's the ROI? Here's my theory: Google is known to be developing a new operating system from scratch called Fuschia[1]. Many many OSes have died in the crib because there was no app ecosystem for them, and thus the cost of switching to the "new thing" was too high for users. How do you solve this problem? Maybe if you create a cross-platform app development framework that lets developers write for the two incumbents while also ensuring compatibility with your new OS...

[1] https://9to5google.com/2018/01/23/what-is-google-fuchsia-os/