There are other factors at play at Wikipedia too. In my native language, Danish, Wikipedia is all but dead. Years ago, I tried contributing within my own field. I researched and spent hours adding relevant information to different topics, only to find out a few days after that all my contributions had been deleted by the administrators.
Here is the Danish site for one of the most beloved Danes: https://da.wikipedia.org/wiki/Michael_Laudrup
Here is the English: https://en.wikipedia.org/wiki/Michael_Laudrup
It's just one example, but it is true for culture, history and many other areas. If you want to know anything on Danish matters, the English Wikipedia is usually a much better option than the Danish.
I think that may be a problem for Wikipedia in such countries. People can read/write English good enough that they just go directly to English.
It's pure speculation on my end though. But I'm a non-native English speaker but I never go do my native language's Wikipedia.