I don't know, honestly.
My harsh assessment is that Mozilla has developed a culture of quitters -- they kill products long before they've had a chance to thrive.
Wikimedia, on the other hand, is an intrinsically conservative ecosystem. I don't know if it has the culture to try new things. They may try cutting their way to success, too, like with the shutdown of Wikinews.
https://en.wikinews.org/wiki/Wikimedia_Foundation_closes_Wikinews_after_21_years