The link between Covid and hydroxychloroquine lies in an immune system condition called “cytokine storms”. These cyto storms are basically the body’s over-response to things like certain viral infections and can cause organ failure.
Covid appears to be triggering these responses in many people who are getting incredibly ill and needing respirators. Hydroxychloroquine is a rheumatoid arthritis drug that was also approved to treat cyto storms in cancer patients a few years ago.
As far as the data for treating severely ill Covid patients goes, I haven’t looked too deeply. On the surface, it appears mixed, incomplete, or too early to make a definitive answer.
I could be wrong, but that’s how I understand it anyway. And as stated in previous posts, we as Americans are not above simplifying the facts to fit our own political narratives.
Here’s a couple links:
https://en.m.wikipedia.org/wiki/Cytokine_storm
https://www.forbes.com/sites/claryestes/2020/04/16/what-is-the-cytokine-storm-and-why-is-it-so-deadly-for-covid-19-patients/amp/