I wonder why French doesn't show Morocco and Algeria? In both countries, some 30-50% of people speak French.
But this information is buried deep down in Google and Facebook and is sometimes outright illegal to disseminate (like in French vs Dutch at the level of Belgian municipalities).
Before Cambridge Analytica scandal Facebook business accounts had access to numbers down to a few thousand with regards to the interface language.
I remember that some 80% of Ukrainians used Russian as interface language in their Facebook, and in Brussels, Dutch was on par with English.
For most Ukrainians, Russian is (was?) a happy medium between being a language that they understand, and a language that is well supported in localizations.
I speak en-GB but I prefer an interface in en-US. Yet if you asked me to speak en-US with all its grammatical, lexical and phonological differences intact I would fail because my understanding is read-only.
Ukrainian vs Russian is a cultural choice. I sm sure that 80/20 ratio is old news by now, anyway.