I think this is the greater challenge now for Google. A system being very well designed and implemented only attracts enthusiasts and people like that with free time. Even the 'better security' aspect doesn't convince the majority of developers. For general usage in IoT and primarily in smartphone/tablet devices, Google would have to:
1. Port ART together with all of Android's public facing APIs to Fuchsia. Evidence says they are doing it, at least for Android ART. As people say, "there's no way without Android app compatibility"...
2. Convince OEMs to switch to Fuchsia platform instead of Linux. That I believe is under way with project Treble, or at least has a path for a possible solution. And Fuchsia's architecture solving Linux big pain points would be a strong argument in convincing OEMs to switch. Woundn't be easy though as drivers would have to be (re)developed or some bridge would have to be built.
With above done, developers would have a push to develop targeting Fuchsia natively. Then Fuchsia's better system architecture together with security advantages would be more strongly perceived by end developers.
If Google managed to develop some new fancy end product on top of Fuchsia that got traction, then that process would be a lot easier for them...
The classical chicken and egg problem every platform has but in this case even more obvious because there are no consumers yet so the number of producers is also small.
