I don't think the army actually would have had much legal power. Maybe in the context of a state of disaster like now, but early on it really needed to be overseen as a police operation complemented with health professionals and private security. This appears to have been the system in NSW and has worked well so far. It's all hindsight I know, but when you combine the failures with reports of senior public servants internally warning of deficiencies and calling for the police, as early as March, it's a failure on a whole new level.