Its been discussed at length in the medical community and the consensus is that we kind of didn't realize just how dangerous such a disease was until it was too late.
Conspiracy theorist types think that's bullshit and the government ignored it or whatever, but think about how complicated the disease is in the first place. First you get this weird virus that doesn't seem that contagious (its literally too fat to be sucked up by mosquitoes or begbugs despite being bloodborne) and, at first, seems to have no effect at all on the human body.
Then a bunch of people start wasting away from it. Some normal people, but also a lot of homosexual people who were, due to the attitudes of the time, probably leading pretty self-destructive lives. Same with drug addicts and their used needles. Most doctors were probably like "Let's get you off the heroin and you'll feel way better." But then these people didn't. Then more and more non-selfdestructive people started coming down with this mysterious wasting illness. And in some people, HIV doesn't even activate into AIDS for a long time, so to some extent it was ignored as a cause.
I know there's all those crazy stories of like sex tourism and unclean medical practicies and stuff, but even then this mysterious illness was probably attirbuted to things like sepsis or other forms of infection from unclean medical instruments and poor doctor hygiene.
Plus, when you're dying of AIDS, its not the HIV that's killing you, its all the diseases you immune system normally protects from having a buffet now that your defenses are destroyed. Doctors probably diagnosesed case after case of well-known or conventional diseases in AIDS victims before finally realizing something was seriously out of the ordinary. It wasn't until later on that finally someone figured out that HIV once activated devours your immune system.
In short, I think we figured it out about as soon as we could. There were fuckups and ignorance along the way that slowed things down, but HIV/AIDS is a slow, insidious killer. It wasn't like people were puking up blood and dropping dead in the streets from it like Ebola.