In the beginning the AIDS virus was much the same as it is today, infecting humans. This virus has a great propensity for adaptation, so over any period of time changes form somewhat. The intervention by aliens of the Service-to-Self orientation was one of knowledge, directing the individuals interested in such a tool to the simian creatures harboring this virus, and directing the individuals further in the manner of isolating this virus. Sophisticated isolation was not required. The virus was in the blood, and blood is a natural component of the diet of those initially infected. Infected simian blood was mixed with blood naturally occurring in the diet. This was done surreptitiously. This was a mass assault on the immune system of the ingestor. The virus took hold. Use of this means of infection was no more difficult than the initial spreading methods. Eating bloody meat, poorly cooked, and promiscuous sex were practices occurring intensively. One just, shall we say, went with the flow.
The men in the CIA who gave The Call to our counterparts were of the Service-to-Self orientation to a high degree. Had they not been of this orientation they would not have been approached by the aliens who answered their call. These aliens do not squander their time idly. Their objective in assisting these men was the misery they could spread. Agony, a sense of abandonment, rage and the desire for vengeance, all these emotions work to bring recruits to their orientation. This was the object of the aliens assisting in the spreading of the AIDS virus. The goals of the men who made The Call were many. We will mention some, but it would be impossible in this medium to list them all. In addition, as most of the goals were personal, they are insignificant. The men who made The Call were offered a bribe. They were assured that they could possess the continent of Africa, which is rich in natural resources and human cultures easily dominated. In fact, any humans possessing this continent could expect to be enslaved, so the joke, as you say, would be on the men from the CIA. The aliens they were working with are not known for clarifying their goals.