This letter to the editor of The American Journal of Medicine from 5 physicians strongly suggests that it is the synergy between hydroxychloroquine and an antibiotic that makes the treatment so successful.
When people look at treating a viral infection like SARS-CoV-2, they assume that the antibiotic helps because there could be opportunistic bacterial infections. But what if there is some other synergy going on like the alkalinization described in the letter?