When affluent, urban gay white men
[1] started dying of rare opportunistic diseases, it caught the attention of the medical community. If you read the timeline that I linked, and if you read the rest of the article that you linked, I think you would agree that it seems pretty clear that people who were not affluent, urban gay white men, were dying of AIDS for decades before the first cases were identified.
Low income people, people of color, people outside of urban centers, or those without good access to healthcare, people in third world countries, isolated cases of some exceptionally rare disease isolated first world communities, none of these cases raised red flags.