The fact that Fuschia is a large project without any public purpose, roadmap, architecture process, or governance invites these theories. If you want to be so mysterious you can't complain when people speculate.

From what I've seen, I believe that Fuchsia is intended to eventually replace GNU Linux based Android as the mobile platform for Google... eventually. The idea is to have a good platform for VR/AR apps (soft real-time processing / rendering), while providing a system that can be continually upgraded.

Unlike the current situation with the Android ecosystem right now, where a newly released product is lucky to get even a few security updates in a year or so, and have effectively had support dropped after that.

Compare that to the ChromeOS ecosystem, where Google guarantees 5 years of support from the time the first production on a platform was released.