How about providing an insightful dumbed down summary for us old dummies?
Likely the easiest summary...
“the spike was designed to attack”
Well, remember that AIDS patients have lowered immune function? That’s because HIV kills their T-cells, which are kind of the immune system’s jack-of-all-trades weapon. They aren’t specialized in fighting a specific infection, like antibodies, but can help fight many different threats. Once you lose those, the rest of the immune system is not able to respond as effectively to threats it hasn’t encountered before.