- Emacs - Java IDEs may look better, but this doesn't seem to be an issue for author. Also other tools are very mature for such youn language as Go.
- Goroutines - Java has no built-in equivalent or one opinionated way of green-threading, only frameworks requiring months of expertise. From perspective of person, who need to switch language quickly this is very discouraging.
- No inheritance - Java design patterns are clearly no-no in the described context (they were presented as anti-pattern).
- Built-in, effective templating - again one easy path to start with, also powerfull enough to write your own tools if needed.
Go is simply easier/faster to start with and most of the performance problems were not GC-bound, so JVMs maturity wasn't such an advantage.