It doesn't sound it was ever planned to be shipped? It was for experimentation, research and development. And some of that work made its way into Windows. Seems like a success to me.
edit:
> Midori was the code name for a managed code operating system being developed by Microsoft with joint effort of Microsoft Research. It had been reported[2][3] to be a possible commercial implementation of the Singularity operating system, a research project started in 2003 to build a highly dependable operating system in which the kernel, device drivers, and applications are all written in managed code. It was designed for concurrency, and could run a program spread across multiple nodes at once.[4] It also featured a security model that sandboxes applications for increased security.[5] Microsoft had mapped out several possible migration paths from Windows to Midori.[6] The operating system was discontinued some time in 2015, though many of its concepts were rolled into other Microsoft projects.
Hopefully Fuchsia doesn't succumb to the same second-system effect.