D had Andrei Alexandrescu behind it for years, he worked at facebook for a while and tried to push D there, and they did used D for while

Andrei is a big deal i would say

Since then FB moved on the build their own Ocaml based language reasonml

Julia doesn't have a big company behind, yet the language is steadily climbing the popularity ladder (and i doubt they have anyone at the calibre of Andrei Alexandrescu, but again, good pogrammer is not a good program manager)

D is not popular, because its leader failed at making it popular, they failed to give the qualities that would make it popular