The number of patients already overwhelmed the healthcare system.

Per some interview with some Chinese doctors who battled COVID19, they said that for many critical patients, their viral load is actually low, but the virus had caused damages to all parts of their bodies thus antiviral isn't going to do anything significant at that stage.

This might suggest chloroquine could be helpful at earlier stage of COVID19, to help prevent patients developing into server/critical stage, which would still be a very good thing if hold true.