It was being used for 40 years as on off label w/o trials by most doctors for lupus and arthritis.
And malaria. But it isn't without risks, some serious. When pharmas want to repurpose drugs that already exist, they must do trials to show effectiveness.
In this case, they might have been able start administering the drug immediately, and put off the trial till later. Thing is, it... DIDN'T WORK.