I’m sorry you think I’m knowledgeable about Islam… I feel like in the last couple days I’ve just demonstrated how little I know.
There are a number of Muslims who find the study of Mahdi prophecies very fascinating, and they know more in detail. It doesn’t fascinate me so I’ve not done much to study it. I did check some sites before posting, though, and found that there happen to be many ahadith about the Mahdi, many of which have the highest level of authenticity for a hadith, that they are multiply transmitted.
It just happens to be a topic that is perhaps somewhat confusing for many people and thus not approached at lower levels, and only discussed among scholars and things. I don’t know for sure. It’s certainly widespread, just not everyone is very informed about it (like me.)
If you can, you might be able to find a lot more information on this particular subject among the Shi’a–because the Mahdi is supposed to be from the family of the Prophet Muhammad, it would be likely they would have more information on the subject.