“Lookit, AIDS exists all over the planet. Yet only in Africa is it a huge problem . Why?”
One reason is ignorance of many things but one story in particular that I read some time ago stated that there was a theory that if a Man with aids had sex with a virgin he would be cured. I don’t remember which country in Africa it was but that Old Wives tale was leading to many rapes and thus more infected people.
That is a provable explanation, and the most likely one.
Superstition, ignorance, crimes such as rape are all rampant in Africa.
As for the origin of aids likely from monkeys, it only makes sense. Eating monkey brain/ meat is a delicacy in some tribes.