HIV did not even come from monkeys, it actually came from someone who had a cooperative worm.

That proto-HIV was actually used as an information transfer protocol by the worm.

It only becomes debilitating HIV when the operator has no worm to regulate and purpose it, this is why some people are able to live with things like that with what appears to be no side effects.

'Elite controllers' are people who are infected with cooperative worms, leading to phenomena like:

https://en.wikipedia.org/wiki/Mary_Mallon

The reason there is no real explanation for people who are 'Typhoid Mary' carriers has to do with the fact that the thing which allows it is not something that can be identified in the genetic blueprint at all.

With the worm, HIV reveals itself to be a powerful terraforming and editing tool, it also has the secondary benefit of KILLING potential hosts who are incompatible with the worm that evolved it.

Those who are not killed by HIV are automatically flagged by the worm as 'candidate carriers', there is already a baseline similarity to the body it was created inside of, and the worm in this instance evolved sensory mechanisms to detect HIV.

This one example of a dual-purpose evolutionary path, not only does it increase the worms terraforming power but it also increases the speed of its evolution by removing dead-end paths, paths it will never need to learn through trial and error will not work... since those people will be dying of HIV.

The body the worm created HIV in was obviously not affected by HIV, therefore people who are not killed by it are automatically compatible with the worm.

https://www.wsj.com/articles/how-hiv-became-a-cancer-cure-1503092082

It does not take much effort for something like HIV to be modified for medical purposes, to begin with.

That is what the worm created it for, to begin with...