Where did he call it the "greatest breakthrough"? I mean, it's of the greatest convenience if there's a chance that a cheap ubiquitous drug can damage COVID's operation in a host, and I think I can forgive him for talking it up in that context (and btw, always with disclaimers), but I don't recall him calling it the greatest breakthrough. Could be wrong but would expect a source.
Also would take issue with "significant risks". HCQ, especially in the temporary loading dose being used in COVID cases, is largely, largely, largely benign except for edge case patients. I do remember Trump saying multiple times in the briefings that people shouldn't take the drug without their doctor's prescription. Presumably prescriptions being given out to people in the edge case risk category would have their doctors to blame, not Trump.
I'm all for calling out shaky medical advice, but the dangers of HCQ being published in the media were overblown, especially considering the context of a pandemic. To pretend otherwise is just rhetoric. Like with autoimmune diseases, the doctors say that while there's risk from long term use of HCQ over a certain daily dosage, considering it may prevent you from dying via organ failure, the narrow and reducible risk is worth the payoff. If you're dying of COVID and a doctor decides it's your best chance, you're not going to give a shit about long-term usage risks, and let's presume your doctor will weigh short term risks accordingly.