Well, "somehow", Android phones are sold in these countries, and while Android devices are not truly "open" by any respects, they almost always are able to let you "sideload" absolutely any sandboxed app you want... including these apps that are banned in all of these countries that Apple insists they are forced to block. The reality is that Apple is only forced to block them because they have decided to be a centralized arbiter of all content for these devices, something that Google and Samsung did not do, and so have created a powerful, centralized bottleneck that can be leveraged as a tool for regimes to control their population. The only reason this is thereby happening is because of Apple's greed: they would rather be able to collect 30% of every transaction that occurs on their systems than to add a trivial feature--sideloading--that would fight against and undermine this oppression.
I highly recommend watching a talk I was giving a few years back--the best version being when I did it at Mozilla Privacy Lab (link below)--which focuses on the ramifications of the core of this problem across the industry (but of course, with one of the narrative focuses being on Apple, as I have a lot of background knowledge there).