Fuschia is not a desktop OS. It's designed for lower end or embedded hardware. Besides, Android has the highly profitable app ecosystem so it makes more financial sense to build GoogleBook based on that.
> Zircon targets modern phones and modern personal computers with fast processors, non-trivial amounts of ram with arbitrary peripherals doing open ended computation.
Fuchsia also had a Linux compatibility layer similar to WSL1 at some point. Might still be there?
[0]: https://fuchsia.dev/fuchsia-src/concepts/kernel/zx_and_lk
Also, that was an easily citable doc line, but I think a more comprehensive look at the work done in Fuchsia shows it has or had ambitions to run on personal computers.
e.g.: fancy graphics stack, Linux compatibility layer, ideas about OS integrated cloud syncing, the original work on the Xi text editor.