Two fold plan. Show Shake is used, make Shake accessible.
Accessible
Translator from Makefile.
Compatibility for Ninja, CMake.
Nice pretty website.
Docs.
Active stackoverflow community and mailing list.
Technicals
Show Shake is practically useful, and if using it practically shows up failings, fix them. Need more companies who use it to declare so.
Need to convert the GHC build system to Shake, as it's Haskell, and if they won't use Shake, no one will.
Convert some big open-source project, ideally Linux kernel.