proud tatty,
Chazal are not Hashem and it borders on Avoda Zorah to impute Hashem’s powers to Chazal. Would you say that Chazal knew of the Holocaust was coming but said nothing beacuse they knew the source? of course not. They are not deities and are not perfect.
To use your analogy, medicine now allows us to cure many more people , thru medicines or technology, than were possible centuries ago. Clearly these were permissable because Hashem allowed human beings to invent them for the betterment of Jews in particular and all mankind. So, why didn’t Chazal tell everyone about them, since they knew about them? Why don’t they cure cancer? I realize that that there are no answers to these questions, just as believing that the Chachomim are not perfect and all-knowing does not diminish on’e emunah in Hashem