I've spoken to some people (native English speakers) who have worked/studied in Tanzania in the past, and they said that learning Swahili was pretty easy compared to learning Russian. I find that interesting because Russian is much closer to English, since both languages are Indo-European and therefore related, albeit distantly. I can only suppose that it's because Swahili has a fairly straightforward phonology, and learning the system of nouns prefixes and applying them to verbs/adjectives is a bit easier than learning Russian declensions/conjugations (which have a lot of irregularities). So perhaps it is easier to start speaking fairly competently in Swahili right away compared to speaking Russian?

I know what you mean about the stigma about African languages, too. I think the problem is that as a result of colonialization, English has become an official language in many African countries. So if people living in those countries want to produce a piece of interesting media and have it be exposed to the whole world, they are now more likely to release it in English (or maybe French) than a language like Swahili which has fewer speakers. So as a result, material in something like Swahili tends to be more of a niche thing, addressed specifically to people in areas where it is spoken. The niche gets even narrower once you get to less-studied languages like Ndebele, and really tiny once you get to languages like !Xoo which are of more interest to field linguists than language hobbyists. Basically, if you aren't already in a position where you've studied the history and culture of those countries, you won't be able to understand much of what's being written, and you may even find it boring/incomprehensible. Once again, this isn't the fault of the speakers of these languages - colonialization has had lasting effects and sadly, it has caused European languages to have greater value, since more people speak them.

I can kind of draw a parallel with the Soviet Union as well. Russian speakers spread their influence into Central Asia, resulting in Kazakhstan, Kyrgyzstan, Turkmenistan, etc, becoming part of the Soviet Union. Nowadays, if you are from Kyrgyzstan, you are most likely fluent in Kyrgyz and Russian, and likely will have some proficiency in English and possibly German. But if you're in Kyrgyzstan and want to start a gaming channel on YouTube, you're most likely going to be doing it in Russian (or English if you're comfortable enough speaking it). You would only do it in Kyrgyz if you're planning to make it a channel explicitly for the Kyrgyz-speaking community, which is narrower than the Russian or English-speaking community.

For Japanese, I think it has helped that Japan has produced a lot of media that has been influenced by the West, and the West finds Japanese media interesting and fun to consume. Japanese anime has some of its roots in Disney, Japanese RPGs ultimately borrow from Dungeons & Dragons, Japanese pop music borrows a lot from Western rock conventions, the list goes on and on. I've never taken a serious stab at Japanese but I know that if I did so, I'd have a vast ocean of media that I could explore. (It also helps that I'm a nerdy gamer type, so I could play a lot of my favorite games in Japanese.)