a) HCQ must be given early (~3-4 days or less after symptoms begin) hopefully before the virus has significantly damaged the mouth, throat and lungs. Once the viral damage is done then HCQ efficacy declines rapidly.

b) a zinc supplement is given with HCQ. HCQ helps zinc to enter the cell whereupon the zinc halts/slows viral replication.

c) an antibiotic (e.g., azithromycin) is given with HCQ, not to stop the virus but to halt opportunistic bacterial infections that might otherwise enter tissue damaged by the virus.

So you can see why many hospitalization studies showed HCQ ineffective: those studies waited far too long to use HCQ.

It is claimed that such delays are a technique used in drug trials to discard possible inexpensive drugs and promote other patentable and therefore profitable drugs. See R.F. Kennedy Jr.'s book for details:

https://www.amazon.com/s?k=THE+REAL+ANTHONY+FAUCI

The Real Anthony Fauci: Bill Gates, Big Pharma, and the Global War on Democracy and Public Health

by Robert F. Kennedy Jr.