Why are the posts there in English?
That's not even true in my European country, I'm pretty sure at most 50% of Iranians speak English (not even taking into account that to write comfortably you need B2 or better English proficiency).
Any kind of English-only media is automatically ignored by 90% of my countrymates, because most people prefer their native tongue.
eg getting upset on someone else's behalf, for something that doesn't actually bother them
The internet/computers were never designed for Farsi. And the situation was way worse for phones before smartphones. It’s only recently that efforts have been made to make it possible to communicate via Farsi, Arabic, or South Asian languages. But it’s still extremely hard.
Russia has a significant Russian only computer development program, so communicating over devices via Russian is more common. East Asian languages have spent a lot more time/energy finding ways to communicate via their own languages, and even there, the most popular text communication language is one which uses English characters. Also, English is spoken far less than in a country like Iran, which has a highly educated populace, that until very recently was very integrated with the English speaking world.
Communicating in English is absolutely obvious for such a diaspora.